As games like Guitar Hero and Rock Band have grown increasingly mainstream, so has the music inside the game. Most of the songs in the original Guitar Hero were covers, but newer games like Guitar Hero 5 and Rock Band 2 spoil would-be musicians with albums from some of the greatest artists in history – The Rolling Stones, Bob Dylan, Linkin Park, they're all there. Prominent bands like Aerosmith, Metallica, and The Beatles even have their own branded titles. So many great bands have appeared in a rhythm game, it's easier to make a list of who's missing.

U2

U2 has won more Grammys than any other band, and lead singer Bono was nominated for the Nobel Peace Prize for his miraculous leaps against global poverty. This ALMOST makes up for us not being able to thrash along to "Beautiful Day" without a single guitar lesson, or even putting on a clean pair of pants. Last year, mild rumors of an entire U2 edition of Guitar Hero circulated gaming blogs and magazines, yet would-be Edges still await an occasion to break out their wool hats. Given the super group's penchant for political protest songs, however, perhaps it's best only select songs make it to Guitar Hero. Surely there are better ways to honor Irish civil rights casualties than mastering "Bloody Sunday" on expert.

What it would look like:

Prince

When asked during an interview why he has yet to appear in Guitar Hero, The Purple One replied, "….I just think it's more important that kids learn how to actually play the guitar. It's a tough instrument — it's not easy…. you just have to stick with it, and it's cool for people who don't have time to learn the chords or ain't interested in it, but to play music is one of the greatest things." It's no secret Prince is getting older, but who knew he was already at the, "new technology is ruining society" stage of life? Pretty soon he'll be offended by his own music. According to a survey by Youth Music, 2.5 million kids picked up real guitars and drums after playing music-themed videogames. Prince, I don't know if you're reading this, but that blue underlined text signifies a link to another website. Welcome to the future.

Led Zeppelin

Led Zeppelin's glaring absence from the world of Guitar Hero isn't because of money or a principled stance against plastic instruments. According to The Wall Street Journal, Jimmy Page is uncomfortable letting other people handle the band's master tracks. Perhaps one day we'll see an all Led Zeppelin themed Rock Band game, complete with Lord of the Rings-esque fantasy imagery on every screen. Perhaps we can get a Guitar Hero with all the classic blues tracks Zeppelin borrowed and incorporated into their own music, or at least a Mario-esque platformer about the fantasy sequences in The Song Remains the Same.

What it would look like:

Johnny Cash

Johnny Cash's voice is so distinctly tied to the folksy, fast-paced rhythm of a giant acoustic guitar, it was downright creepy in 2002 to hear him wail along to the sparse "Hurt" without wall-to-wall chords and drunken, hooting bull-fiddle players to back him up. So why haven't the legendary opening twangs of "Folsom Prison Blues" or "I Walk the Line" mosied into any existing Guitar Hero? Classic country has been a largely ignored genre within Guitar Hero soundtracks. Ignoring Pantera's misleading "Cowboys From Hell," the Guitar Hero franchise's deepest foray into deep Southern rock is "Devil Went Down to Georgia," which is kind of like going to Florida and never leaving the Epcot Center.

Phish

A band primarily known for their live act, irregular meter, unusual chord progressions, and extended improvised 'vocal jams' ordinarily wouldn't scream Guitar Hero. Then again, Phish is no ordinary band. Every member of Phish is among the best with their respective instrument, so there's always something interesting cooking. Plus, think about all the money they could make selling a vacuum cleaner peripheral.

What it would look like:

Frank Zappa

If you want Frank Zappa in your game, you're going to have to get through The Zappa Family Trust. The unusually aggressive trust is run by Frank's widow Gail, and handles the licensing for all of Frank's music. In the past they've sent cease-and-desists to Zappa tribute bands, Zappa blogs, and a German Zappa memorial festival called "Zappanale." They haven't made any public comment about why music from Frank Zappa's 60 albums has yet to appear in a videogame, but maybe everyone's just afraid to give them a call. It's a shame. Frank Zappa once said, "If you're a musician, play my music. If you're not a musician, play my music." For the first time ever, Guitar Hero makes that possible.

What it would look like:

Velvet Underground

On first glance, an experimental rock band influenced by minimalist composers and Edgar Allen Poe might not seem like ideal Guitar Hero candidates. And sure, their songs about death and drugs might be a little grim and dark. And sure, the Velvet Underground haven't sold that many records. However, Brian Eno once said that while hardly anyone bought Velvet Underground records, the ones that did formed their own bands. If the mathematics of Brian Eno apply, putting "Sweet Jane" in the next Guitar Hero could lead to the number of kids who pick up musical instruments after playing Guitar Hero jump from 2.5 million to 6 billion.

—Additional writing by John Townsend