Classical music is littered with examples of this trope; pieces of music considered revolutionary at the time they premiered would often spawn scores of imitators, sometimes to the point of changing musical tastes and convention the world over. This isn't just true of music that was well-received upon its inception, either; Igor Stravinsky's The Rite of Spring was so controversial that the audience at its premiere rioted, and yet it's been so influential in the modern era that much of 20th-century orchestral music might as well be called "The Rewrite of Spring".
Ludwig van Beethoven: Established the idea of a composer as an individual instead of a tunesmith working for the Church and/or the government. Without him the entire Romantic period in classical music might never have happened...
Louis Armstrong: His popularity showed many Afro-Americans that the white establishment would give you status, money and artistic merit if you started a jazz band. Similar joyful jazz performers such as Cab Calloway also own a lot to him.
Gene Krupa: Drummers become an important part of jazz bands thanks to his wild way of playing the instrument.
Muddy Waters: First blues singer to use electrical guitars to provide a heavier sound. Also the first one to not simply sing about melancholy, but also pure erotic lust. Both very influential on later blues artists, as well as British blues/rock groups like The Rolling Stones, Eric Clapton and Led Zeppelin,...
Elvis Presley popularized rock 'n' roll to a huge world wide audience. Various Elvis like artists all copied his hairstyle, way of dressing and took up a guitar to perform rock songs.
Chuck Berry's frenetic guitar playing has been copied by every early rock guitarist. Only Jimi Hendrix had perhaps a larger influence!
Little Richard's exciting performing style has equally inspired many rock artists ever since.
Similarly, after Buddy Holly and Ritchie Valens were killed in a plane crash in 1959, American record companies scrambled to find teen rockers to fill the gap. Many were signed, but none had the talent or innovation of these two, and the evolution of rock music was stalled until the British Invasion. This time in rock history may also qualify as a Dork Age.
After their big American debut breakthrough and their continuing world wide fame afterwards countless Beatles imitators popped up. Most of them especially copied the mop-top hairstyle, comedic antics and sometimes even fake British accents. Even those who didn't directly copy them were inspired to start a rock band just because of them.
The Monkees were also based on the Beatles (not just musically; the show was originally pitched as a serial version of A Hard Day's Night), but the wildly different influences of the four Monkees and their assorted music producers & TV directors broke them out of Follow the Leader mode before the first season had ended.
The film A Hard Day's Night also became the blueprint for every "good" teenage rock movie ever since. A lot of music videos owe a lot to the way director Richard Lester set the Beatles' music to exciting images.
The idea of a rock group re-inventing itself after each new album was more or less invented by The Beatles. Especially in the 1960s and 1970s a lot of famous bands like The Who, The Rolling Stones and Pink Floyd tried to experiment with new sounds, styles and themes on each album.
In Japan there was a whole new genre born out of these attempts, the Group Sounds genre, which lasted roughly half a decade before being replaced by the New Rock spinoff genre, but not before birthing a number of popular bands such as The Tigers (Kenji Sawada's big break), The Tempters (The Rolling Stones to the Tigers' The Beatles), and The Spiders.
Bob Dylan popularized folk music and "authenticity" as a musical artist. He became the first pop artist with a much larger emphasis on personal, meaningful lyrics than musical accompaniment, widely imitated by several artists ever since, from John Lennon to Leonard Cohen.
Black Sabbath's success in the early '70s propelled heavy metal into mainstream pop radio. Blue Oyster Cult, which had little in common stylistically with Sabbath, was dubbed "the all-American Black Sabbath" by its producer in an attempt to cash in on the craze.
Though New Edition actually came first, the Boy Band craze of the nineties was actually started by New Kids on the Block in the late 1980s. These pre-fab moneymakers seemed to be "built" from a mix of stereotypes: one or two pretty boys; a rebel with tattoos (rehab optional); the crazy one who gave the really funny quotes in the interviews; one who could actually sing, but looked funny; the sweet, down-to-earth one; and the schmoe. For the most part, good looks and flashy dance moves were a bigger priority than actual musical ability. Pop Culture Isolation is also likely why NKOTB is known for starting the Boy Band craze as opposed to New Edition, even though their music was hardly different.
Maurice Starr was the svengali behind both NKOTB and New Edition, both bands based around the Boston area.
Of that vintage, only Alanis Morisette is still a legitimate popular star, after starting to use her full name and becoming Darker and Edgier. Alanis was only a teen pop star in Canada. In fact, once she became famous in the States, her management and record company did everything in their power to block her earlier Canadian material from being released in America, in order to preserve the "edgier" image they had created and were cashing in on.
Britney Spears lead the wave of "teen pop starlets" into the new millennium (thank you very much, Total Request Live). She continued to pick what sounds came along before they hit the big time till right now.
Billie Piper began her career as a teen pop starlet. After a brief music career, a marriage to DJ Chris Evans, and a few years' gap, she now has a respectable acting career. Doctor Who was not her first TV part.
The Mickey Mouse Club is to blame for many pop artists of the late nineties, most notably Spears, Anguilera, and several members of *NSYNC and the Backstreet Boys.
The boy band trend spilled over into country music. Rascal Flatts was a boy band with a steel guitar on their early albums.
The success of Hanson, an at-the-time pre-teen Bishounen boy band (they were, however, truly a band, as all sang, wrote or co-wrote their own material, played their own instruments and had input into their material and image from the start) and their major label debut Middle Of Nowhere, and infectious Jackson Five-like number one single, "MMM Bop", released in 1997 at the height of grunge and nu-metal, was also very influential in the popularity of teen-pop in the late '90s.
Another trend that begin at the turn of the millenium. The "Latin Boom." It started with Ricky Martin and Jennifer Lopez, and then there was a long string of people singing in both English and Spanish (Shakira, Marc Anthony, Thalia, Paulina Rubio). Even Christina Aguilera got in on the game.
In fact, Coldplay themselves are often accused of ripping off Travis and/or Radiohead. So was Muse, but they essentially became an alt-prog band after their second record.
In the same vein, much of the late-90s to mid-2000s Top 40 alternative/rock music is essentially knocking off the previous "alternative band", and those surrounding them, which are all knocked off of the basic chords of Canon in D. While you can blame Kurt Cobain for the phenomenon, it was almost definitely started earlier. Still continues to this day, as much of the radio and Top 40 is virtually indistinguishable from each other. Parodied hilariously by Rob Paravonian's "Pachelbel Rant" (easily found on Youtube).
Back in The Nineties, after Nirvana really blew up, record labels scrambled to sign any act that was even remotely grunge-y. The absurdity reached a fever pitch when Sony Records went all the way to Australia to sign Silverchair, whose members weren't even old enough to shave. It worked.
Nirvana also led to the signing of many acts that were underground, but not grunge, such as Green Day. This occasionally led to incredibly mainstream-unfriendly acts getting signed (Boredoms, anyone?). Those acts seldom lasted long on the labels, however, which was probably for the better, as they didn't have to worry about being screwed by the label.
Similarly, after Mötley Crüe and later Bon Jovi and Poison became huge, record labels signed every Hair Metal band they could find to cash in on them. One extreme example involves MCA's signing of Pretty Boy Floyd when they had only played eight shows at the time!
Other bands signed by major labels were packaged as hair metal bands despite the fact that they weren't. Power Pop band Enuff Z'Nuff were dressed in vaguely psychedelic glam clothing by their label and appeared in glammy music videos. This unfortunately caused the average music fan to get an incorrect perception of what the band actually sounded like, much to the lament of the critics that adored them.
Although there's considerable confusion over exactly what style of music Korn popularized — some say Rap Metal, but only about 5 songs in the band's entire 8-album career have rap in them — it's generally agreed that a lot of bands followed their lead. Hence, they made an album called... Follow the Leader.
After 2pac's death loads of rappers tried to duplicate his image and music (minus the socio-political commentary)
Once Bone Thugs-n-Harmony became popular a lot of other rappers emerged with a melodic R&B styled rap delivery (minus the speed).
After Jefferson Airplane, Jimi Hendrix and The Doors hit big in the late 60's, major labels signed every psychedelic act they could find. Some found genuine talent: The jazz label Verve Records signed The Velvet Underground and Frank Zappa. Warner signed the Grateful Dead, although they used their contract to make three wildly uncommercial albums before making their two classic records in 1970 (after which, they promptly split from the label). And EMI, looking for a band that sounded similar to the Beatles' new psychedelic sound, signed a small psychedelic band called Pink Floyd. Other labels weren't so lucky and were stuck with multi-million dollar contracts with one hit wonders like The Strawberry Alarm Clock, The Ultimate Spinach, Bubble Puppy and The Electric Prunes.
Amy Winehouse inspired a retro-blues movement that includes Duffy, Adele, Paloma Faith, and possibly Sharon Jones and the Dap Kings. She also led to a major resurgence in the popularity of female singer, songwriters in general all over the world, with the likes of Lady Gaga, Florence Welch and Jessie J all of whom have emerged since Back to Black's release crediting Winehouse with paving the way for them and making it easier for them to have mainstream success.
In the 1990s, the "hat act" craze was in full bloom in country music. Many young, hot acts were kicking off their careers in their mid-20s like George Strait did, and usually wore cowboy hats, jeans and pressed shirts just like George. While this gave the genre many talented megastars in the likes of Alan Jackson, Clint Black and Garth Brooks, it also gave the genre plenty of bland radio fodder pretty boys. Over time, "hat act" became a derogatory term.
A more positive example started by Strait was the return to a more traditional, fiddle-and-steel sound following the crossover-happy early 80s. This led to very hardcore, neo-trad acts such as Randy Travis, Ricky Skaggs and the aforementioned Alan Jackson, while concurrently decreasing the success of more pop-sounding acts such as Ronnie Milsap, Kenny Rogers and Alabama.
Similarly, the success of Brooks & Dunn in the early 1990s led to the creation of countless mainstream-sounding singer-songwriter duos, none of whom came even close to touching Brooks & Dunn's success — most couldn't even get a Top 40 hit. For nearly 20 years, the "Duo of the Year" category at the Academy of Country Music and Country Music Association was a mere formality. Things didn't turn around until 2006, when Sugarland (who, despite being another singer-songwriter duo, has a more diverse sound) finally snagged a Duo award. B & D retired in 2010.
Shania Twain opened the door for country-pop crossover females, although more of them followed Faith Hill and Martina McBride sonically (slick pop production with lots of belting). However, the bottom has fallen out so hard that virtually no female artist besides Carrie Underwood (herself a country-pop belter), Taylor Swift and Miranda Lambert can even get beyond the top 30 at country radio.
Gretchen Wilson's "Redneck Woman" and to a lesser extent, Jason Aldean's "Hicktown" both seem to have started the long-lasting trend of hard-rock country songs in which the singers assert that yes, they are country singers because they listen to Merle Haggard and George Jones, they wear boots and worn-out jeans, they're bad boys/girls who love their mamas, etc. Most singers were brought to this by way of John Rich of Big & Rich, who wrote the aforementioned songs but has mostly backed off from songwriting.
In general, whenever a secular music artist becomes popular and spawns imitators, the Christian Music industry will take notice and scramble to find bands and stars to fit the mold, so Christian kids will have "wholesome alternatives" to whatever's popular in the secular music biz. Sadly, this often means that several genuinely good, unique Christian bands get completely ignored, or go Indie when their label pressures them to mimic a popular style.
Emo music first started in the 80's and has changed a lot since then, but more recently the enormous mainstream success of angsty hardcore-influenced bands such as The Used, My Chemical Romance and Taking Back Sunday seems to have proven that emo teenagers are a good audience to target. Thus every cookie-cutter pop punk act now has to over-straighten their hair, have the odd tattoo or piercing and wear eyeliner and overly tight jeans. See Metro Station, Boys Like Girls, etc.
In the early to mid 90's R&B acts followed 2 archetypes. One type was the 4 to 5 member group type with gospel-inspired harmonies ala En Vogue and Boyz II Men. The second type followed the 2 to 3 group member formula that was based on a edgy, sexually explicit street/Hip-Hop look and sound ala TLC and SWV (the latter toned down their look though). Some were terrible rehashes and copycats. While others were good in their own right.
Groups like H-Town and Jodeci were a unique (at the time) fusion of the 2 aforementioned archetypes.
In 1978, the album Van Halen was released with Eddie Van Halen's fretboard-tapping "Eruption" heard round the world. Two years later, Randy Rhoads' playing on Ozzy Osbourne's Blizzard of Ozz cemented fast, classical-inspired guitar playing known as "shredding" as the new standard. Every lead guitarist in heavy metal—and many even in hard rock and pop music—had to play blazing fast solos, preferably with fretboard tapping, until the rise of grunge in the early 90s killed off the trend.
Composer Anton Bruckner's huge, massive, overwrought symphonies directly influenced Gustav Mahler's even bigger works, as Mahler was a student at the Conservatory and attended concerts at the Vienna Philharmonic that premiered Bruckner's works.
A lot of the post-disco, new wave funk/electro funk/synth funk bands that came out of the late 70's early 80's that died a quick death fall under this trope (though the whole subtly racist "death to disco" residual backlash also might be to blame, but that's a different can of worms). The more popular ones were groups like Cameo, Zapp Band, Debarge, Evelyn King, and The Gap Band, but the rest came and went, bands like: The Jets, The SOS Band, (for all intents and purposes were a 2 hit wonder), Skyy, The System, Starpoint, Midnight Starr, The Force M.D.'s, Klymaxx, Ready for the World, and Kleer. Although it's debatable on whether or not they weren't better than the other bands that did get huge, cause quite a few of these groups have a significant cult following. Partially due to being Sampled Up.
Michael Jackson's Thriller videos were a game changer for the music video industry. Up to that point, videos were mostly glorified concert performances and few included dancing. Jackson introduced sensational dance moves and line-dancing with other dancers, something that was quickly copied by almost every popular music artist afterwards. While he is often credited with creating the concept of, well, the Concept Video, those existed before Jackson — what he did popularize were big-budget, special effects-heavy examples of the form.
A decade earlier, the clip to Bohemian Rhapsody by Queen is widely credited with popularising the idea of the Concept Video, a music video that was anything other than just a performance of song. (It wasn't actually the first, but it was the first one to really get attention for doing this and inspire imitators.)
Janet Jackson could be credited (or blamed) for sowing the seeds of the raunchy Stripperific R&B dancer types. Starting with Aaliyah (although she was tame by today's standards) who then paved way for people like Ashanti, Ciara, Rihanna, Brook Valentine, Mya, Christina Millian, so on, and so on. Some say Adina Howard helped too. Before her some would point to Vanity/Appolonia 6. Making this Older Than They Think.
Christina Aguilera's critics like to point out how she seems to be hopelessly behind every trend in pop, the standard 90's pop at the start of her career, the Rnb/Rock/Pop/Jazz second album, the 40's 50's 60's sounds which were popular only 5 years before and Bionic, it's electronic pop sound which happened four years prior never exactly hitting the trend when it's at it's trendiest. "Bionic" was a big blow to her image and her way of working and took the sheen off her for a lot of people.
The main complaint people have with Metallica's Load and ReLoad records is that their music stylings were uncannily similar to the grunge/alternative bands that were popular at the time (albeit with an obvious blues/country influence).
After T-Pain started using Auto-Tune to make his voice sound robotic, so did… well, nearly everyone else.
The Sex Pistols launched punk in the U.K. and inspired countless people to start their own band solely based on attitude and less on skills.
The success of Bob Marley paved the way for many reggae artists to copy his look, musical style and dabbling with rastafarian ideas. Even non-Jamaican artists!
Equally rap and hiphop music went through its share of shameless imitators as well. Let's see:
The trend in rap of mainly bragging about your decadent lifestyle and using stock phrases such as "you know what I'm sayin'" has also been copied by almost EVERY rap artist nowadays to the point that they have to "prove" whether they are "keeping it real or not".
Thanks to how huge Mumford & Sons have gotten in recent years, there has been a huge resurgence of Folk Music such as the Lumineers, Of Monsters and Men, Edward Sharp and the Magnetic Zeroes, the Avett Brothers, and more trying to capitalize off of Mumford's success. note Some of these bands, such as the Avett Brothers, have been around earlier than Mumford but only got more attention after Mumford got big.