If you're looking for the scale that ranks the hardness of ''actual'' rocks and metals, Wiki/{{Wikipedia}} [[https://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness has you covered.]] This one is about music.

Basically, a scale for ranking the "hardness" of music, "hardness" being the perceived quality that separates rock from pop, HardRock from soft rock, HeavyMetal from HardRock, DeathMetal from classic metal, noise from {{Grindcore}} and {{industrial metal}}, and so on and so on.

As of late, the scale has been expanded to include genres related to rock and metal such as ElectronicMusic, blues, jazz, and country. The scale also encompasses long-established musical standards such as pop[[note]]though the examples provided are, of course, rock-influenced[[/note]] and ClassicalMusic[[note]][[OlderThanTheyThink which actually predates rock]] in being "hard", or "heavy", as proven by many classical pieces made before the rock age[[/note]]. It should be noted that songs from these genres do not usually make it to the scale; those that do are usually similar to or influenced by rock or metal.

Unfortunately, it's kind of a difficult concept to pin down, but trying as hard as possible:
* More guitar distortion is the easiest measure of this. This is also the defining factor that separates metal from rock and rock from other genres: guitars in metal sound metallic due to the amount of distortion, while guitar riffs in rock usually have a warm, bluesy quality as opposed to the "happy" pop sound. It's a bit difficult to classify those rare offshoots from rock that don't use guitars. Meanwhile, bands who play other aggressive non-metal styles that may incorporate screaming like screamo, post-hardcore, hardcore punk, or noise rock use loud guitars, but don't tend to have the signature "metallic" riff style of playing and/or tuning that defines metal, which is the reason why metal is almost always considered separate from other forms of rock. Instruments other than guitars, such as synths, pianos and bowed strings can at times match the timbre of distorted guitars if played aggressively, but they don't necessarily lend themselves to sounding hard.
* Production quality can play a role. Generally, albums with a [[ThreeChordsAndTheTruth raw, unrefined sound]] lend themselves to sounding hard, and tend to fall towards that end of the scale. Some genres such as [=grindcore=] take this to extremes and deliberately aim for a difficult listening experience as part of their aesthetic. However, as with all of these rules, exceptions can be found, and some of the very hardest bands can have an extremely polished, technical sound, where hardness is distinguishable mainly by other factors.
* Louder and faster are good, but not definitive measures for this. Generally slow, quiet songs are softer than loud, fast songs, but there are definitely exceptions, though as a rule most hard songs are either loud or fast if they're not both. [[DoomMetal Funeral Doom]] and [[DroneOfDread Drone Metal]], for example, are both ''extremely'' slow but make up for this with ''extreme'' loudness, while other extreme genres break up loud sections of songs with quiet sections that nevertheless maintain speeds much greater than most pop music. Additionally, there's an important difference between "loud" and "hard", as a consequence of the LoudnessWar and variable production techniques - a lot of hard rock and good old fashioned heavy metal has gotten ''louder'' over time as re-released albums tend to be remastered with increased loudness, but this does not make them harder, while a death metal cover of a classic metal or rock song probably ''would'' be harder[[note]][[http://www.youtube.com/watch?v=LBax7oePHfo Witness]].[[/note]].
* The overall mood and atmosphere that songs provide to listeners plays a very important role in the measure of a song's hardness. Songs that are more upbeat and energetic tend to fall in the softer ranges of the scale, while darker and more subdued songs are obviously harder. There are most definitely many exceptions all throughout the scale; thrash metal, power metal, electronic/rock crossovers and many varieties of modern {{metalcore}}, such as melodic metalcore and metallic hardcore, feature upbeat songs and vigorous muscianship but tend to fall towards the harder end of the scale. Similarly, some theme music from MagicalGirl series creep up to the higher reaches of the scale due to a combination of soaring instrument work and lively musicianship typical of most HeavyMetal songs. [[note]] The Anime/PrettyCure franchise is most notable for this.[[/note]], and even some extreme metal bands (especially those that fall under MelodicDeathMetal or GrooveMetal) play lively, energizing songs with tempos and melodies akin to pop rock or punk rock. Conversely, baroque pop and dark ambient are generally dark and unsettling to, with tempos akin to DoomMetal, heavy orchestration and the occasional OminousLatinChanting but fall towards the lower end of the scale. The existence of genres where MoodWhiplash is a defining feature (such as classical and progressive metal) makes this measure of hardness a little less definite; in such cases hardness can be measured by other factors.
* How [[DarkerAndEdgier dark and edgy]] the lyrics are, sometimes taking RefugeInAudacity. This is really only tangentially related to how hard the song actually is, but it's really the best measure if you can't figure out exactly how much distortion is on the guitar. A song titled [[http://www.youtube.com/watch?v=T0YifXhm-Zc "She Loves You"]] is going to be a lot softer than a song titled [[http://www.youtube.com/watch?v=MuV-Aq1PwqU "Blunt Force Castration"]]. Of course, many examples at the LyricalDissonance page exist to subvert this phenomenon, and instrumentals avert this rule altogether. See the sister trope, MohsScaleOfLyricalHardness, for details.
* Certain instrumental techniques are more commonly found in heavier rock or metal than in softer varieties: double-bass drumming (where the drummer uses two bass drums, or two bass pedals) is practically ubiquitous in extreme metal, but rarely heard in rock, for example. Similarly, many metal guitarists make heavy use of techniques such as palm muting, tremolo picking and tapping, which tend to be used sparingly, if at all, in rock.
* A sometimes-useful measure is how conventional the rhythms and melodies are. Most rock, pop, blues, dance music etc., is based around a simple 4/4 or 2/4 backbeat, (occasionally 6/8 or 3/4), and use either a blues scale or a diatonic scale. By contrast, prog-metal or experimental bands make heavy use of unusual rhythms and time-signatures, and extreme metal bands tend to ignore melody for the most part (with exceptions like [[MelodicDeathMetal Melodic Death]] or BlackMetal, and sometimes [[TechnicalDeathMetal Progressive Death Metal]][[note]]where melody is usually quite complex, but is mostly deployed as a musical device rather than as a central element of composition[[/note]]). However, both unusual melodies and rhythms are very common in some forms of softer music, especially jazz: Dave Brubeck's "Take Five", for example, could easily fit into #1 on this scale, but is written in the very unusual 5/4 time signature with an unusual key signature.
* An often reliable measure of musical hardness is how low the instrument tunings are. Many forms of rock and metal music often employ minor keys, atonality, and dense riffing that are often achieved through the use of dropped tunings; hard rock and heavy metal, in particular, feature liberal use of dropped tunings such as Drop D or Drop C, Some musicians, especially in extreme genres such as DeathMetal and IndustrialMetal even go as low as Drop B or Drop A create a thick, heavy sound, and many of them may even use seven or eight-string guitars to simulate the effect of extremely low tunings or go even lower (sometimes a full octave down from standard tuning). There are exceptions to this; BlackMetal musicians often make use of higher tunings to create a piercing guitar tone, and {{Industrial}}, [=grindcore=] and metallic {{dubstep}} musicians may not even care about how their instruments are tuned; instead they rely on sheer atonality and abrasive sounds to achieve very high levels of hardness.
* As noted below, vocal style (singing, belting, shouting, screaming, or growling) is a good measure of hardness, not merely in the style used but in how frequently a particular style is used. It's not especially uncommon, for example, for modern alternative rock artists to use singing predominantly and screamed vocals on occasion, while more mid-range hard styles like metalcore may make extensive use of shouting, while deploying death growls infrequently to add a darker tone to some passages. If, on the other hand, screams or growls are used ''constantly'', or as the main vocal style with softer, clean vocals used only to ''lighten'' some parts of a song, you're probably looking at at a substantially harder band.
* Song structure plays an important role in determining overall hardness; most pop and rock songs often use a fairly predictable verse-chorus-verse structure, with a bridge thrown in before the final chorus, whereas most mid-ranged heavy metal songs break up the pattern slightly with strategically-placed solos or breakdowns, and heavier forms of music opt for more complex structures. Musicians from certain genres such as mathcore and IndustrialMetal may even ignore typical song structures altogether for a more chaotic sound. However, song structure alone cannot make a song heavier or softer: some very heavy songs consist of ''[[StrictlyFormula nothing but breakdowns]]'', and genres such as GothRock, baroque pop, ClassicalMusic and especially jazz tend to ping lower on the scale despite the complexity of the song structures.

Rough outline of the levels:
# As soft as rock (and to an extent, most music) gets. May be an otherwise 2 song without any guitar to distort, or a song which is generally slow and light. Most acoustic music, baroque pop, and DreamPop can be found here. Additionally, folk without a significant rock influence is mostly here.
# Soft rock and most pop. A lot of early rock can be found here. This is also the level where guitar distortion starts to appear. The lighter end of ClassicalMusic can also be found here. Pop ballads begin at this level. PostPunk starts appearing here. The softest AlternativeRock is found here.
# Rock sans intensifier. A bit faster/louder/darker than 2, but still pretty soft. The heaviest soft rock and the softest hard rock and dance-punk can both be found here. PopPunk begins at this level. Most of the songs in this level come across as more "radio-friendly/MTV-friendly" than those on higher levels. Cinematic music/film score starts at this level. Most "danceable" ElectronicMusic (especially the lighter end of {{Eurobeat}}, [[HardcoreTechno happy hardcore]] and {{trance}}) end up at this level. This is also the home level for {{Synthpop}}, [[NewWaveMusic New Wave]], and {{Disco}}.
# Relatively harder rock. This is where distortion-driven rock starts to become the norm, though mostly clean/acoustic guitar songs are also common. This is about where you can start finding punk, as well; lighter than this and you can't usually muster the kind of anger you need for punk. The harder, more bombastic end of ClassicalMusic, especially the works of the great composers, can also be found here. Lighter PostGrunge also begins to show up here. This is pretty much as heavy as Rock n' Roll got, though the vocal SurfRock gives some of the earliest examples of this level in Rock. This is also home to the slightly heavier dance-punk bands such as Music/LCDSoundsystem and The Rapture. This is probably the last level where you're likely to find CountryMusic without a significant hard rock influence.
# Hard rock that is definitely still rock. This level was first pioneered by instrumental SurfRock, but it wasn't until PsychedelicRock (primarily The Music/JimiHendrix Experience and Music/TheWho) that it was widely explored. The love songs start thinning out here, but lyrics at this stage can be about just about anything. This is also where mid-range post-grunge and the very heaviest dance-punk (e.g. Death from Above 1979, Music/ElectricSix and Music/DoesItOffendYouYeah) can generally be found. This is the last level where you can find classical music that does not have electronic or modernist elements. Baroque pop at this level often incorporates elements from harsher music genres. Discounting ballads, HairMetal starts here [[note]]of course, the hair metal at this level usually has more in common with Hard Rock than metal [[/note]], think Music/DangerDanger or Saraya. This is mostly as high as PostPunk gets. With a few exceptions, this is usually the higher end of mainstream CountryMusic as well.
# Difficult to tell if it's rock or metal. This is pretty much as far as you can get on just an acoustic guitar or any non-electric instrument. This is also about as hard as you can get while remaining in pop territory, and about as light as you can get while being undeniably metal. HairMetal and classic {{grunge}} can often be found here. Most AlternativeMetal starts showing up here. The lightest ProgressiveMetal shows up here. The lighter end of {{Industrial}} music shows up here. This is the last level where you can find film score that does not have a metal or electronic infusion. This is also the level where ClassicalMusic transitions into neoclassical and symphonic metal[[note]]See Nightwish and Within Temptation's examples at this level[[/note]]. This is usually the highest level you'll find pure PopPunk, past this point its usually infused with either metal or hardcore. It's also generally the final level where regular AlternativeRock appears. On average, this is where most AvantGardeMetal and other experimental or "weird" (such as psychedelic trance) genres can be found.
# Classic metal and most PowerMetal. This is also (mostly) the point where Punk transitions into Hardcore Punk. The music is pretty fast and noisy at this point. The lyrics start to become darker, though clean and melodic (often classically trained for Power Metal) singing is still standard, usually saving harsh vocals for occasionally [[SopranoAndGravel emphasizing the contrast between styles]]. The heavier sides of Glam and post-grunge can be found here, as well as much NuMetal. Viking and FolkMetal start showing up around here. The lightest GrooveMetal can be found here. AlternativeMetal with more emphasis on the 'metal' part starts showing up here as well as most ProgressiveMetal. Most metal/electronic crossovers either begin here (metallic dubstep and drum and bass) or end here (hard trance, tech trance, {{Speedy Techno Remix}}es, and Eurobeat). Metalcore will only occasionally be found here, but when it is, it usually lacks harsh vocals, save for a token scream or two (think, most of Music/AllThatRemains recent songs, or most old Avenged Sevenfold) or the occasional {{yarling}}.
# Most ThrashMetal, and heavier forms of PowerMetal along with some classic metal. HairMetal tends to creep into this level as well (think of early Music/XJapan or Music/{{Loudness}}). Lyrics are usually very dark at this point. Vocal style is usually a snarl (most thrash metal uses this singing type), but clean singing is also common. Occasionally [[HarshVocals growls]] and [[MetalScream screams]] will be employed. Most hardcore punk is here, as well as the lighter end of {{metalcore}} and crossover thrash (fusion of thrash metal and hardcore punk). Whether purists want to hear it or not, the lighter and more atmospheric side of BlackMetal also starts here as does very light MelodicDeathMetal. Grunge and post-grunge occasionally creep into this level as well. You'll also find yet more viking/folk metal populating this region. Most GrooveMetal is here. In general, this is also pretty much as hard as you can get with significant radio or MTV play or if you want your song featured in VideoGame/GuitarHero or VideoGame/RockBand. AlternativeMetal or NuMetal at this level usually has a lot of influence from more aggressive metal genres. The heavier sides of ProgressiveMetal can be found here. Of the Big 4 of Thrash, Metallica, Megadeth and Anthrax were often found here, at least when they were still unambiguously thrash. This is also the point where pure {{Industrial}} and IndustrialMetal begin to sound almost indistinguishable from one another.
# Lighter DeathMetal (especially MelodicDeathMetal) or harder ThrashMetal. Most experimental metal groups creep up to this level as well. You'll also find a lot of the less abrasive 'true' BlackMetal here. To the uninitiated, songs at this level and beyond could be NightmareFuel in musical form. Here is about where you start to get singers [[HarshVocals growling]] or [[MetalScream screaming]] for most of the song; this is also probably the highest level that can be attained with clean singing as the main vocal style. Lyrics may be very violent or just generally extremely dark. This is the last zone where you are likely to find hardcore punk that doesn't have a substantial metal or noise infusion. {{Metalcore}} continues to be found here, as well as the lighter end of {{deathcore}}. This is also pure HardcorePunk[='=]s absolute peak of hardness in the scale. Most viking/folk metal that has a significant infusion of BlackMetal or DeathMetal falls here. A lot of the heavier side of GrooveMetal is found here. ProgressiveMetal at this level often incorporates extreme metal elements. PowerMetal can be found here, but it almost always involves crossover with other genres at this point (see Music/ScarSymmetry and Music/ChildrenOfBodom for examples). This is the home level of the three big melodeath bands (Music/InFlames, Music/AtTheGates and Music/DarkTranquillity) before they changed styles, as well as Music/AmonAmarth and later Music/FleshgodApocalypse. Similarly, of the big four of thrash, this was Slayer's playing field most of the time[[note]]Although at their time they would've been the prime level 10 example.[[/note]]. In regards to Industrial, however, this is the home level for some EBM/Electronic Body Music[[note]]See Combichrist and Auto Aggression's examples at this level.[[/note]].
# This is most DeathMetal and BlackMetal[='=]s home level. Lyrics start to get positively disturbing and/or {{gorn}}y and the singer will always be growling or screaming, though clean vocals can be used for [[SopranoAndGravel contrast]] or [[OneWomanWail for]] [[OminousLatinChanting sound]] [[CreepyChildrenSinging effects]]. The hardest variants of ThrashMetal,[[note]]especially German thrash metal[[/note]] MelodicDeathMetal,[[note]]See the examples from Septicflesh and The Black Dahlia Murder at this level[[/note]] and viking/folk metal can hit this point, but that is quite uncommon. At this point hardcore bands become indistinguishable from metal to anyone who's not a loyal fan of both genres, since hardcore at this level is blatantly influenced by metal. Likewise, Thrash Metal on this level can sound pretty close to Death Metal to the uninitiated. At this point HardcorePunk becomes {{grindcore}}, and while it is possible for a {{metalcore}} band to get this high, it's very rare, although this is Music/{{Chimaira}}, Music/{{Converge}} and Music/TheDillingerEscapePlan's home level, and Heaven Shall Burn often reaches this level as well. GrooveMetal at this level usually has a lot of DeathMetal influence.[[note]]See the examples from Chimaira, Fear Factory, [=DevilDriver=], Gojira, Meshuggah, Pantera and Slipknot at this level.[[/note]] {{Dubstep}} with a significant metal infusion ("metalstep"/"brostep") can also be found here.[[note]]Most of Music/{{Skrillex}}'s harsher output resides at this level.[[/note]] This is also where you start to see Funeral Doom, Drone Doom, and Death/Doom.
# UpToEleven: Music/AnalCunt is here, along with the harder side of [=grindcore=] especially the subgenres of pornogrind, noisegrind and goregrind. The most extreme DeathMetal (examples from the brutal death metal and slam death metal subgenres usually end up here) and BlackMetal [[note]]See Teitanblood's, Deathspell Omega's and Anaal Nathrakh's examples at this level[[/note]] also lies here. The very heaviest mathcore (technical[[note]]e.g. Ion Dissonance, Music/TheDillingerEscapePlan[[/note]], chaotic hardcore[[note]]e.g. Converge, Death Dust Extractor[[/note]]) can also reach this level. Most recently, DoomMetal has also managed to climb to this level; in recent years this level has become the province of death/doom, funeral doom, and drone metal[[note]]See [[Music/SunnO Sunn O)))]]'s and Music/{{Khanate}}'s examples at this level.[[/note]]. Crossovers of HeavyMetal and electronic music rarely get up to this level, but this is home to power electronics and most hardcore techno (especially speedcore and noisecore), and most of the hardest IDM/Braindance[[note]]See Autechre's, Venetian Snares's and Squarepusher's examples at this level, you will see...[[/note]], the most extreme drum and bass[[note]]Level 11 dnb will often have monster speed and may sound near-indistinguishable from industrial music to most people. Music/{{Noisia}}[='=]s harsher output resides here, for example.[[/note]] and dubstep[[note]]Level 11 dubstep will have a very harsh drop, heavily distorted bass and hardly any room for breathing. This is Music/{{Excision}}[='=]s home level, but other dubstep musicians such as Flux Pavilion, Doctor P, Skrillex and Devilman have managed to creep up here.[[/note]] can be found here too. Songs at this level often invoke auditory SensoryAbuse in [[HellIsThatNoise all]] [[BrownNote its]] [[ScareChord forms]], and can quickly become MostAnnoyingSound incarnate to many listeners. [[HarshVocals Growling]] or [[ScreamsLikeALittleGirl screaming]] will always sound [[TheUnintelligible unintelligible]] and almost inhuman, and often pitch-shifting or other computer-aided effects are used to drive the vocal range beyond what could normally be sustained during singing[[note]](astoundingly though, [[http://www.youtube.com/watch?v=6ObHhRnvCqk not always]])[[/note]]. Cleans are virtually absent, but if cleans are present, they'll usually be a haunting OneWomanWail or OminousLatinChanting. Drums are so fast that it sounds like a ''solid wall of black noise'', or are so slow that a snare hits at the first second and the next beat ''never comes.'' Guitars and bass are heavier than a black hole, the heaviest known object in reality, and will (almost) surely sound like a chainsaw. Any and all electronic instrumentation will sound like a mess of chattering noise and beeping sounds. Production plays a ''very important'' role at this level: it may be [[ThreeChordsAndTheTruth extremely raw and low-fi]], or [[LoudnessWar highly polished but intentionally brickwalled to deafening levels]]. In other words, [[WesternAnimation/{{Metalocalypse}} the music is blacker than the blackest black times infinity.]] Significant elements of this class are [[TrueArtIsIncomprehensible experimental]] in nature, although [[StealthParody stealth parodists]] commonly make their way up here as well.

* While each level represents a certain standard of musical hardness, within each level, some songs may be harder or softer than the established standards. This variance among songs within levels leads to each level being split into 5 subcategories: Borderline (straddles the line between two levels), soft ([[ExactlyWhatItSaysOnTheTin a soft example of a level X song]]), standard ([[CaptainObvious average example]]), solid (a particularly relevant example of the music's hardness at a certain level, it is harder than standard, but softer than hard), and hard (an obviously harder example). The soft and hard subcategories are subsequently split up in other two subcategories, very soft and soft; hard and very hard.
* A [[http://m-ex.deviantart.com/art/Devio-Evolution-of-Metal-Fans-234264835 very well exemplified illustration]] of different levels of metalheads and the most stereotyped opinions.
* The scale primarily gauges the "hardness" of music in genres that are usually perceived by many as having a quality of "hardness or softness", and is named as such because '''rock''' and '''metal''' music are the two genres that exemplified and defined musical hardness. Songs from the two aforementioned genres are the usual standards as to which songs can be classified or put on the scale, which means that while songs outside rock and metal do make it to the scale, they are usually subjected to stricter/more thorough listening and comparison to standards than usual.[[note]]Songs outside of rock and metal that are usually "guitar-driven" do make it to the list faster than those that aren't; such examples usually come from some varieties of ElectronicMusic, pop, and neoclassical[[/note]]
* ''Lower hardnesses are not bad''. Remember, Music/TheBeatles come in at 2-3, and 9 (or above) can be difficult to listen to, especially for people with sensitive ears. Likewise, ''higher hardnesses are not bad''. Remember that even though it may sound like impenetrable noise to you, that doesn't mean in principle it isn't enjoyable, nor that it doesn't contain real musical sophistication and talent.
* As time goes on, those rock/metal bands at the top of this chart go to increasingly insane lengths to top one another or themselves, which causes the chart to compress itself to accommodate the new hardness. So a 6 now could be a 4 or 5 ten years from now, an 11 may become a 10, a 1 may disappear altogether, and so on.
* Level 11 exists in general for the placement of any music that is [[UpToEleven definitely harder, louder, darker, or noisier than what is common at 10]]. While this may seem obvious, the important distinction to make is that anything at 11 should still exist within an easily identifiable genre, such that a familiar listener should easily be able to place it as [=grindcore=], DeathMetal, BlackMetal, DoomMetal, dubstep, IDM or whatever genre it may draw from. What stops it from being a 10 is merely that it takes an [[UpToEleven additional step beyond]] what is popular in any given year within the 10 range of albums, either in terms of an increasingly raw, chaotic sound or in terms of sheer speed, or progressive technical brutality. In fact, one of the key and most helpful descriptors of level 11 is the word "[[MindScrew crazier]]", which is often the way it sounds to most listeners until the style gains a bit of popularity and moves down into 10.
* Corollarily, anything beyond 11 (and to a lesser extent, the harshest and most abrasive Level 11 material) starts to fall under [[HarshNoise Noise]]. Noise is a category for [[GenreBusting unsortable]] [[NeoclassicalPunkZydecoRockabilly experimental]] music that is extreme in ways other than being "heavy" in a traditional fashion. Anything by most Noise artists (with a few exceptions from Music/{{Merzbow}} and Music/MariaCross) is guaranteed to go off the high end of the scale. There really are no identifiable guitars, basses, drums, or even vocals,[[note]]Or there may be one or two discernible instrument sounds but are played in an unlistenable manner[[/note]] and the music tends to become overwhelmed with extended techniques including computer sound manipulation. Here artists (and listeners) are mainly interested in exploring the limits of what can be interpreted musically, whereas at 11 listeners and musicians are merely interested in pushing the boundaries of existing genres. However, the [[SensoryAbuse genre-fucking mutability]] of things like Level 11 {{grindcore}}, {{industrial}}, noise rock, [[{{Dubstep}} brostep]] and mathcore tends to create ambiguity in this respect.
* Conversely, anything below 1 is too soft to go on the scale, owing to a lack of audible/perceivable hardness. Minimalistic forms of music such as ambient, background/furniture, space music, and Gregorian Chant belong here. In such forms of music, there are discernible vocals, pianos, strings, basses, percussion, etc. but are arranged in such a way that the hardness is virtually inaudible, resulting in a very light, empty sound, or played at a very low volume that it comes across as inaudible. Similarly, genres such as show tunes, lounge music and bubblegum pop tend to be too lighthearted and commercial-sounding that the "catchy" bits suck out most (if not all) of the perceivable hardness (as well as the "substance" that can contribute greatly to a song's overall "feel"). Below Level 1, listeners are merely interested in "hearing" songs as opposed to getting a "feel" of how a song sounds. However, the softness of genres such as Level 1 classical, film score, ballads and baroque pop somehow make the lines a little less distinct.
* In general, a band will have songs that are higher or lower on the scale than their usual level, hence why websites like Wikipedia put some bands and/or albums as both rock and metal. (Compare [[http://www.youtube.com/watch?v=wlVdPl-oEmg "Tourette's"]] and [[http://www.youtube.com/watch?v=IPSYplu_3fA "Polly"]], both by {{Music/Nirvana}}.) It's easier to just judge each song by itself. You also have bands that [[NewSoundAlbum change their style]], often becoming [[DarkerAndEdgier heavier]], [[LighterAndSofter softer]], or becoming a genre that's [[NeoclassicalPunkZydecoRockabilly much harder to classify altogether]].
* The reason some of the metal FanDumb hates power metal, non-Scandinavian melodic death metal and {{deathcore}} is that the aforementioned genres are exceptions to the above rule that metal bands tend to get harder over time. Likewise, the metal FanDumb tends to hate on some metal-influenced ElectronicMusic styles such as dubstep, power electronics and industrial because such songs rely more on digital manipulation rather than sheer instrumental craziness to achieve high hardness levels. Funnily enough, most of the brostep musicians who reside at the harder end of the scale are actually metalheads.
* Interestingly enough, a live performance, remix, or reissue of a song can actually be a different level than the original studio version, especially if an extended solo(s) or guest musicians are involved. [[LoudnessWar Volume compression]] (which is frequent on recent remasters of old material) may arguably contribute to different hardnesses between releases as well. For example, compare [[http://www.youtube.com/watch?v=fStQd9yFbvY this original version of the]] [[Music/WolfgangAmadeusMozart Lux Aeterna]] to [[http://www.youtube.com/watch?v=SLJllk-0o6c this one]], the latter of which was used in Film/RequiemForADream as a leitmotif. Notice a difference?
* [[ChristianRock Christian Metal]] (despite what some of the Metal FanDumb says) is usually as heavy as its mainstream counterpart; however, in most cases, Christian metal '''lyrics''' aren't as dark as secular metal. So, a song could be a 10 or 11 in musical heaviness, while the lyrics could be about the power of God's love for the world. Obviously not all Christian metal songs are like this, but it's a common part of the genre, and the point still stands. As mentioned above, the lyrics are only indicators and don't play a direct part in the song's hardness, so you don't need to place Christian metal songs at a lower hardness just because of the lyrics.
** Similarly, many of the more [[TechnicalDeathMetal progressive, technical artists]] who reside at the hard end of the scale (Music/{{Augury}}, Music/{{Death}}, Music/{{Neuraxis}}, Music/{{Decapitated}}, Music/{{Origin}}, Music/{{Meshuggah}}, and Music/CephalicCarnage, to name a few) generally write lyrics which, while certainly quite [[SlidingScaleOfIdealismVersusCynicism cynical,]] and [[DarkerAndEdgier darker]] than most at the soft end of the scale, [[LyricalDissonance aren't especially graphic or disturbing.]] Their lyrics are often highly philosophical, reflective, introspective, or merely less visceral as opposed to the outright {{Gorn}} written by many of the other bands residing at the top of the scale (e.g. Music/CannibalCorpse, Music/{{Exhumed}}, early Music/{{Carcass}}). Such exceptions also apply to bands such as Music/NapalmDeath and Music/TheAgonist which write politically or socially conscious lyrics.
** Corollarily, instrumentals and songs with little to no audible vocals are just as heavy or light as songs with vocals.
* Sometimes, songs with symphonic elements can be at a lower level of hardness than they would be without the symphonic elements. It depends on how the elements are implemented in the song, however; some more extreme artists use symphonic elements to provide a contrast between blast beats and the like, and manage to be just as heavy as other conventional death/black metal bands, or in some cases, heavier. Similarly folk elements work much the same way. Sorting these songs out on a case-by-case basis is the best solution.
* Melodic tendencies can play a part in the song's hardness. Similar to the above note regarding symphonic elements, melody can decrease the hardness of a song, but it depends on how it's used, and as such the songs will be handled on a case-by-case basis.
* What's extreme to you may sound accessible, even ''catchy'' to the next person, so level assignments are highly subjective. For example, many tropers place metal ballads in level 6. On the other hand, seeing as how metal ballads typically interconnect softer acoustic/piano passages with harder electric guitar/percussion driven passages (that may otherwise reach into 8 to 9 range), one could just as easily assign them to level 7 or 8, depending on how far one felt certain passages removed the music from a level one felt was enjoyable. This is especially true in the case of [[TechnicalDeathMetal progressive death metal]], where extended [[SymphonicMetal symphonic]], [[{{Jazz}} jazzy]], [[ProgressiveRock proggish]], or [[FolkRock folkish]] passages are commonly interlaced with full-on level 10 or Level 11 blasting. Consider [[http://www.youtube.com/watch?v=6DlWQr8wYvY "The Lair of Purity" by Augury]] and [[https://www.youtube.com/watch?v=XhohQNdSt7g "The Lotus Eater" by Opeth]] by way of example: are these songs brutalising extreme metal, or are they lighter and gentler progressive metal?
* And even within a song, there can be some parts that tend to be lighter or heavier. This tends to be seen more often in EpicRocking songs and [[NeoclassicalPunkZydecoRockabilly experimental]] compositions. Some songs start off light and gradually become heavier, while others start off really heavy and soften from then on. Then there are songs that [[MoodWhiplash shift from light to heavy]] with [[ScareChord extreme suddenness]]. As a general rule, it is recommended to listen to a particular song from start to finish before making assessments and putting them in the scale.
* Songs by progressive, experimental, and avant-garde groups tend to be more difficult (or impossible) to classify. Some bands make a point of changing tempos, dynamics, and style to portray a wider range of emotions and ideas, as well as using sharp contrasts to make heavy moments seem heavier and vice versa. This naturally becomes more common with longer songs (see Music/{{Rush}}'s 2112 in level 6 examples), as twenty nonstop minutes of either blasting or light swing could easily be boring to the point of unlistenable. Classical examples include Music/{{Yes}} and Music/KingCrimson, while more recent projects such as Music/TheFallOfTroy and Music/MaudlinOfTheWell mix [[SopranoAndGravel clean vocals with growls or screams]]. Bands such as Music/FaithNoMore, Iwrestledabearonce, Music/{{Sigh}}, Music/DirEnGrey, Music/{{Celldweller}} and Music/{{Ulver}} would take NeoclassicalPunkZydecoRockabilly to extreme levels, even going as far as [[GenreRoulette switching from one genre to another]] or [[GenreBusting playing an outright weird form of music]], sometimes resulting in songs that span nearly the entire scale.
* The harder the music is, the more likely it is to fall under RottenRockAndRoll. In a film, show or video game, if both the heroes and the villains play music or have a musical theme, the villains' music will probably be harder than the heroes'.


* MohsRockMetal/Levels1To3
* MohsRockMetal/Levels4And5
* MohsRockMetal/Levels6And7
* MohsRockMetal/Levels8And9
* MohsRockMetal/Levels10And11