By Matt Caputo
By Devon Maloney
By Chris Chafin
By Village Voice
By Katie Moulton
By Hilary Hughes
By Gili Malinsky
By Bob Ruggiero
What Happened?: Jay-Z and Linkin Park teamed up for the groan-worthy 2004 "mash-up" project Collision Course and ended any chance of this being cool ever again. Girl Talk emerged in 2006 with a sound so sophisticated that it made your roommate's hilarious "Fugazi Osbourne" project look even stupider than it was.
Hype Cycle: 2002–2005
Key Artists: The Rapture, Radio 4, !!!
What It Was: A mix of early-'80s dance-y post-punk bands like A Certain Ratio . . . and early-'00s posturing about how you own an A Certain Ratio record.
Creative Peak: The Rapture, "House of Jealous Lovers" 12-inch 
Typically Effusive Praise at the Time: "Bands like the Rapture have sent their message: The rock show was not meant to be a collegiate study. We have all stopped caring what snotty academics find acceptable, because now there is real, true, palpable fun, and it is the greatest liberation." —Pitchfork, 2003
What Happened?: Franz Ferdinand figured out how to get real money, so dance-punk's coolness sputtered to a halt once it spawned watered-down major-label cash-ins (the Bravery), watered-down indie-label cash-ins (Bloc Party), and super-glossy pop cash-ins that still defy all logic (Ashlee Simpson's 2005 single "Boyfriend").
Hype Cycle: 2003–2006
What It Was: Inner-city London kids spawn a mean-mugging, minimal mix of U.K. garage, American hip-hop, Jamaican dancehall, and, apparently, PlayStations eating themselves.
Creative Peak: Dizzee Rascal, Boy in Da Corner 
Typically Effusive Praise at the Time: "Pressing play on the East Londoner's debut was akin to hearing Public Enemy for the first time—all alien sounds and harsh DIY bleeps, plus of course Dylan Mills' brilliantly edge-of-chaos rhymes. MC culture, he showed, could deliver more than pop garage or pallid Americanisms."—The Guardian on Dizzee Rascal, 2003
What Happened?: The indie snobs who stumped for it suddenly realized there's actual American rappers with shitty backgrounds to fetishize (see "trap-rap"). Lady Sovereign got signed to Def Jam and wasted some of Jay-Z's money. Dizzee Rascal started hanging with Calvin Harris, folding grime into a Brit version of the same boring electro coke party that Flo Rida hosts every weekend.
Hype Cycle: 2004–2006
What It Was: Dudes with beards and ladies in flowing dresses playing weird and/or pastoral strum. Pretending you were an animal or child apparently helped.
Creative Peak: Joanna Newsom, The Milk-Eyed Mender 
Typically Effusive Praise at the Time: "This music makes my heart feel stout, and enables me, with my eyes, to breathe fire." —Dave Eggers on Joanna Newsom, Spin, 2004
What Happened?: After curating the scene-defining Golden Apples of the Sun comp, Banhart got all pissy about being lumped in with a scene. He tried to change its name to "naturalismo," but then realized it's probably more fun just to lay low, make records, and occasionally make out with the Queen of Naboo.
Hype Cycle: 2004–2007
Key Artists: Boris, Wolfmother, Dead Meadow
What It Was: Dave Grohl's unexceptional Probot vanity project brought attention to avant-metal label Southern Lord, making it cool for the ironic-ringer-T-shirt set to share warm PeeBeRs with the denim-jacket-back-patch set. Soon, bands like the Sword, Priestess, and Saviours brought all the energy and aggression of metal without zitty geekazoid tropes like "chops."
Creative Peak: Mastodon, Leviathan 
Typically Effusive Praise at the Time: "If Sunn 0))) is the ZZ Top of experimental metal, with matching beards and Gibson Les Paul guitars, Boris might be the Kraftwerk, or the Ramones, or even the Jimi Hendrix Experience, depending on the album." —The New York Times Magazine, 2006
What Happened?: For most people, standing through two hours of Sunn O)))'s fog machine and drone turned out to be "not really my thing." Indie rockers started their own terrible metal bands (David Pajo's Dead Child, Rob Crow's Goblin Cock), and the burnouts nerds laughed at in high school resumed shaking their heads at us all.
Hype Cycle: 2005–2006
What It Was: Delirious, sproinging Bay Area rap music known for its minimalist bounce, odes to going crazy-cuckoo-bonkers, and vast dictionary of slang—including the ever-popular YouTube blooper staple "ghost-riding the whip."
Creative Peak: The Hyphy Hitz compilation 
Typically Effusive Praise at the Time: "It's by far the best party going on in hip-hop right now. . . . It's hard not to hope that the Bay Area's turn is next, that we're just one breakthrough hit away from a hyphy takeover." —Slate, 2007
What Happened?: A 2007 Mercury News piece detailed an array of poor business decisions—everything from signing bad contracts to rappers just straight-up missing meetings—that left hyphy standing alone in its stunna shades.
Hype Cycle: 2006–2008
Key Artists: Justice, Simian Mobile Disco, Boys Noize
What It Was: A term allegedly coined on the Hollertronix message board, "blog house" described the nu-electro sounds, mainly from French labels like Ed Banger and Kitsuné, of electronic bands that sounded like rock bands—a/k/a stuff an earnest 19-year-old blogger wouldn't recognize as the Hackers soundtrack with a Fader co-sign.
Creative Peak: Justice, †