Drums \ Pro Drums: Involves hitting the correct inputs. The normal mode has a bass pedal and 4 drums (one acts as snare, the other three divide tom and cymbal duties). The pro mode adds 3 cymbals, for 8 inputs total, but otherwise plays the same.
Vocals \ Harmonies: Lines on the highway dictate the target pitch level for each syllable of each vocal part (using sloped lines for Melismatic Vocals). Players try to sing to the same note as the lines, but the octave doesn't matter (e.g. singing a C2 while the real singer is in C4 is acceptable).
"Legacy" Guitar\Bass: These guitars have a fret board with 5 (main) buttons and 1 strum bar. When a gem reaches to bottom of the highway, the player must hit the strum bar while holding the fret button(s) that correspond to the gem(s). Without the strum bar, pressing fret buttons by itself has no effect, making this quite different from drum gameplay.
"Legacy" Keys: Could be considered similar to Legacy Guitar with a touch of drums, in terms of gameplay. Here, there are 5 keys, and the correct key must simply be played when the gem representing that key reaches the bottom of the highway (with the strumming mechanic removed). Legacy G\B charts can be played on keys, but fast "strumming" becomes fast repeated note hitting. Conversely, Legacy K charts can be played on guitar and bass, but keyboard chords tend to be more difficult than guitar chords in a 5-button paradigm, especially when played on a guitar controller.
The Beatles (Though Harmonix wasn't willing to give any numbered order, they confirmed that The Beatles are #1, despite their store being separate.)
Blink182note Punk, 90's/00's/10's with 13 song. First released on Jan. 15, 2008 with "All The Small Things." The song happens to be the series' best-selling single, baring the free songs.
Bostonnote Classic Rock, 70's with 7 songs. First released (as DLC) on Mar. 25, 2008 with a pack based around Boston, their only release to date.
Disturbednote Nu-Metal/Metal, 00's/10's with 12 songs. First released on June 3, 2008 with a pack based around Indestructible.
Foo Fightersnote :Alternative, 90's/00's/10's with 30 songs. First released (as DLC) on Nov. 11, 2008 with The Colour and the Shape.
Metallicanote Metal, 80's with 3 songs!]]). First released on RB1 launch day, Nov. 20, 2007 with a small pack, their only release to date. Has also had all their on-disc songs ("Enter Sandman" and "Battery") removed from their respective export.
No Doubtnote Pop-Rock, 90's/00's with 23 songs. First released on Dec. 9, 2008 with The Singles 1992–2003, which was also the week in which the series celebrated reaching 500 available songs.
The Policenote Pop-Rock/Rock, 70's/80's with 11 songs. First released on RB1 launch day, Nov. 20, 2007 with a small pack and an on-disc appearance of "Next To You".
Red Hot Chili Peppersnote Alternative/Rock, 90's/00's/10's with 27 songs. First released (as DLC) on July 8, 2008 with two singles from Stadium Arcadium. Notably one of the few artists to have their songs removed from the RB2 export to RB3 ("Give It Away"), bringing them down from a potential 28. "Dani California" from RB1 had also received this treatment for a time.
The Whonote Classic Rock, 60's/70's/80's/00's/10's with 17 songs. First released (as DLC) on July 15, 2008 with a 12-pack, The Best of The Who (Rock Band Edition), which was the series' first Greatest Hits 12 pack.
Queen is a interesting case since Lego: Rock Band had two of their songs, the inseparable "We Will Rock You" and "We Are The Champions" along with their appearance on RB3 and RB Blitz.
The Foo Fighters are the only artist in the series with 4 appearances on a Rock Band Title ("Learn to Fly, "Everlong", "Breakout," and "These Days.")
Additionally, Dave Grohl appears as a guest drummer for the Queens of the Stone Age in "Go With The Flow" (RB1) and "No One Knows" (RB3), takes drumming duties for Tenacious D in their song "Master Exploder" (RB2) and as a full member of Them Crooked Vultures ("Dead End Friends" on RB3) and Nirvana ("In Bloom" on RB1 and "Drain You" on RB2), giving him 10 appearances in the series' disc titles.
To this day only one band among these has appeared on all three main-disc titles: The Who with Won't Get Fooled Again on 1, Pinball Wizard on 2, and I Can See For Miles on 3. One thing that these three on disc songs by The Who have in common is that that they were in reverse chronological order (70's in the first game, and 60's in the second and third games) and it was during the time Keith Moon was the drummer for the Who.
Doing It for the Art: Harmonix and Rock Band are considered by many to be the smaller-but-classier competitor to the more financially successful Guitar Hero (which Harmonix established). One look at their credentials or interviews does indicate how dedicated they are to, and how well they know, music.
According to their PR, almost every person on the development staff is a musician in a band and Harmonix is their day job.
Well, given the large number of Harmonix bands in the games (Honest Bob and the Factory-to-Dealer Incentives, The Main Drag, Anarchy Club, Bang Camaro, That Handsome Devil, and Breaking Wheel to name a few), it's not hard to believe.
Ubisoft's Rocksmith, on the other hand, is a more than suitable competitor in the "playing with real guitars" department (especially considering that it works with any real guitar rather than only with models made for the game).
There is a fairly amusing case concerning songs named "Walk". One week saw the release of the Foo Fighters hit in the game. The next week saw the release of the Pantera hit of the same name.
No Export for You: Rock Band 2 never got released in Australia. RB1 only came out in Australia and New Zealand more than a year after its original release. And given that you need an original copy of RB2 to export the tracks from that game to RB3... Aussies can only access the nine bonus tracks from that game. Let's just say the importers are doing a roaring trade on that game with those down under. And that was the one game with studio AC/DC track... (There's still the AC/DC Live Track Pack though.)
Sequel First: Axis: Bold as Love from the Jimi Hendrix Experience was released before Are You Experienced (which had some substitutions).
Also, Judas Priest's Screaming for Vengeance, which was the first full album released on the Music Store, came out before British Steel (the latter was the 30th anniversary edition, with live versions of its tracks; however, their in-game year tag is still 1980, when the album was originally released).
So My Kids Can Play: Lego Rock Band features a new "Super Easy" mode (combining No Fail with being able to hit pretty much anything to count as a success) and locks out songs from any previous version deemed potentially harmful to minors from being played. These both are for the youngest ones, so they can play without being exposed to songs like "Holiday In Cambodia" or "White Rabbit".
Getting Crap Past the Radar: That said, songs that are less blatant about their subject matter can still be played. Most of the ones that are more subtle about Intercourse with You get through, though several about violence also make the cut (if you're curious - cartoonish violence, a la "Skullcrusher Mountain" by Jonathan Coulton is acceptable; horror-tinged violence like his "Re: Your Brains" is not).
The filter seems to be a bit hit-and-miss, though - "Uncle John's Band" by The Grateful Dead was playable in LEGO Rock Band, lyrics with the word Goddamn in them and all.
Vaporware: In 2008, Harmonix had announced a Rock Band: Japan, made for the titular gamers and to be co-developed with QEntertainment. Sadly, Word of God said that the idea was scrapped and will unlikely be developed.
What Could Have Been: Rock Band 3 was originally going to have a keyboard instrument. For whatever reason, this was scrapped. Instead, it was given an appropriate substitute, the keytar.