If you’re not familiar with Tap Tap Revenge (you must not own an iPhone, or read our site very carefully), then you probably don’t know that it’s essentially a clone of games like Dance Dance Revolution and Rock Band, redesigned specifically for the iPhone’s unique interface. It’s fun, and incredibly addictive, which probably has something to do with its impressive degree of success.

Tap Tap Revenge has reportedly been installed more than 20 million times (although that isn’t necessarily unique installs) and people have played more than 600 million rounds. Rough estimates put the total install base of the game at one-third of all iPhones currently operating. Considering the iPhone’s success, that represents a hefty payday indeed.

The source of revenue stemming from the Tap Tap Revenge series is varied. Most of the apps themselves cost at least 99 cents, though Tap Tap Revenge 2.6 is free, and artist-specific special editions cost more. But the real money is made from ads in the games, and from a cut of the in-app purchases available in the latest version, which allow iPhone users to buy and download playable, often themed tracks from their favorite artists.

Obviously, Tapulous is the exception, not the rule. The vast majority of iPhone-only devs don’t make anywhere near that kind of scratch, but if nothing else, this simple rhythm game proves the money’s out there to be made.

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iPhone-owning fans of Lady Gaga, rejoice: Today a new version of Tap Tap Revenge, Tapulous‘ iPhone rhythm game phenomenon, hits the App Store, loaded with 14 tracks from the breakout pop star. It’s also the first version of TTR that can be played with the iPhone held sideways during “boss tracks,” which require all four fingers.

The release of Lady Gaga Revenge is actually part of a much larger partnership with Universal Music Group, one of the big four record labels, that will see more Universal artist-branded versions of TTR come out later this year, and a track-purchasing system so TTR owners can buy songs for gameplay via Apple’s new in-app commerce feature. (When that service launches with Tap Tap Revenge version 3.0, cuts will cost you 50 cents each.) Tapulous’ partnership is similar to the one between the major labels and the video game studio Harmonix, which sells singles for play on their blockbuster, Rock Band (which have consequently sold 40 million tracks).

The Tapulous/Universal deal is a pretty big one for an app that launched only last July, first incorporating music from indie artists, then gradually coming out with versions with big-time acts like Nine Inch Nails and Weezer. In that time, TTR has remained among the top 25 apps and earned an install base of 11 million, Tapulous CEO Bart Decrem told me in a phone call yesterday. He credits that continued popularity to the frequent release of new TTR-playable content, and estimates the game has already sold an incredible 4-5 million songs.

Those sales numbers are particularly impressive because up until now, players had to exit out of Tap Tap Revenge to locate and download new content in the app store. Consequently, Decrem estimates only 4-5 percent of Tapulous owners have bought tracks. However, the addition of an in-game purchasing system will likely increase that conversion rate.

Along with new versions of Tap Tap Revenge featuring UMG music, look for Tapulous to expand the game’s online community experience. Tapulous’ Andrew Lacy told me TTR’s chat feature already processes a million messages a day, sent by hundreds of thousands of players who participate regularly. “We’re just scratching the surface of the community in Tap Tap,” as he put it. With that kind of engagement, I wouldn’t be surprised if Universal stars began showing up in TTR chatrooms to promote their Tap Tap music themselves.

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According to comScore, the market research firm behind the recent survey and an accompanying report, Tap Tap Revenge has been installed by 32 percent of iPhone and iPod touch users as of February 2009. That means one-third of the millions who use the App Store have downloaded Tap Tap Revenge at one point or another. I know one company who won’t have any trouble selling advertising space.

The purpose of the survey was in fact to give marketers a bird’s eye view of the App Store landscape. It also revealed some interesting facts about what kind of apps users are most likely to download and use. The top three categories that app users gravitated towards were retail, social networking and entertainment, respectively. Although I’m a little confused by the retail category (I can think of Amazon, and maybe Stanza and the Amazon Kindle app that might fit this description and be widely used), the other two make sense, especially if entertainment is broad enough to include games.

In a report accompanying the survey, comScore also pointed out that people who downloaded apps were likely to occupy mid- to high-range income brackets, who as a consequence probably have a lot more disposable income to spend on things like fart simulators and sexy pen apps. It notes that 35 percent of app store customers were likely to belong to households with an income of more than $100,000, while over 50 percent earned at least $75,000.

Basically, the final takeaway of the report is that advertisers would do well to look at the App Store as a potentially game-changing outlet from which to sell their shiny baubles. With the ad industry facing a crisis and pulling out of print and online sales, the App Store could present an attractive alternative. Since it has proven reach in a much sought-after demographic, and because of the unique content delivery method offered by apps, it avoids some of the usual failings of Internet advertising. There are no ad-blockers for individual apps, and there’s less competition for the viewer’s attention.

Personally, I’m conflicted. I like free stuff, but I hate ads, and therefore ad-supported software. My solution? Offer an ad-supported lite or trial version of all software, and I’ll buy whatever I actually use just to get rid of the marketing material. Any better ideas?

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Guitar Rock Tour has arrived to challenge Tap Tap Revenge‘s rhythm-action throne. The new arrival touts a bevy of terrific tunes to tap along to, plus the option to play drums or guitar, loads of characters and unlockable awards.

While Guitar Rock Tour may be Rock Band squished on to the iPhone, it’s just as loud and rocks just as hard. Whereas Tap Tap Revenge is free, Guitar Rock Tour costs a few bucks ($9.99) and as such is polished better than a factory fresh Fender Strat.

At the core of any decent music-based game is the soundtrack and, while all of the song in GRT are sound-a-likes of the real thing, these are well performed covers and during a frenetic, in-game jam session the tracks come across as hard-rocking and suitably authentic.

Choose your track in Guitar Rock Tour

There’s a real range of tunes too, most of them classics in their own right, from contemporary tunes like Bloc Party’s Banquet across to classic hits with recognizable riffs such as Message in a Bottlee by The Police. Conversely, Tap Tap Revenge is heavy on excellent, yet obscure, indie and electronic artists spiced with a few chart-topping acts like Kaiser Chiefs and The Offspring.

In essence, the soundtrack for Tap Tap Revenge is more experimental and certainly more edgy. Where Gameloft call on a Blink-182 cover for some cool caché in Guitar Rock Tour, the folks at Tapulous feature girl-kissing chart topper Katy Perry’s latest hit in Tap Tap Revenge.

Play drums too in Guitar Rock Tour

One thing that Guitar Rock Tour implements wonderfully is multiple instruments. For each track you’re able to choose between shredding your way to fame on guitar or beating your way out of obscurity on the drums. In particular, playing the guitar is a joy: with chords executed in a smart way and techniques included for hammer-ons and pull-offs.  As a result, it’s far more tactile-feeling than TTR.

Another feature in Guitar Rock Tour that is absent from Tap Tap Revenge (though not necessarily missed), is a Tour mode. After picking a character and signing a cartoony contract, you and your amateur band take to the road, playing tunes across the U.S. and Canada, and rocking your way to stardom.

Along the way you also pick up various awards, meet some odd characters and unlock new tracks to play live. The story is indeed silly, yet it’s great fun and certainly a compelling way of playing through the game’s selection of 17 tunes.

Stylized clarity in Tap Tap Revenge

In terms of the graphics, the aesthetic in Tap Tap Revenge has a stylized clarity, suiting tons of musical genres, while Guitar Rock Tour is designed with a gritty rock feel — it’s like Guitar Hero meets one of those dingy little bars where the bands jam around Hendrix tunes. Effectively, it’s cliché but it works and screams of console-gaming.

But although Guitar Rock Tour clearly means business, there’s a show-stopping bug that lets the entire game down. On tracks that require more shredding and finger-picking, the backing track falls out of sync with the guitar track. As a result, the game suddenly becomes a lot harder to play and the music ends up sounding like a bad covers band who can’t seem to play in time.

The folks over at Gameloft have made a raucous rocker of a music game, with a stomping soundtrack too, and yet sometimes it just doesn’t work. For now, we’d say hold back from investing until Gameloft patches the problem and releases an updated version of Guitar Rock Tour.

In the mean time, grab Tap Tap Revenge, it may not have all the extras of Guitar Rock Tour, but it’s free, plays very well and includes some fantastic tunes too.

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Get ready iPhone-bearing fans of Trent Reznor, a special edition of Tap Tap Revenge has just been released featuring the music of Nine Inch Nails. The game features 16 NIN tracks, from albums Slip and Ghosts I-IV, hand-selected by Reznor himself.

Tap Tap Revenge was one of the first and most popular games on the iPhone platform, and according to some claims boasts more than 2 million users. Tapulous, Tap Tap Revenge’s developer, purchased the game from Nate True, who’d released the original version as Tap Tap Revolution for jailbroken iPhones and iPod touches. The track list for the original release version of Tap Tap Revenge is made up of independent artists, and the NIN edition marks the first time a major label release has been used. This is also the latest in a recent string of attempts on Reznor’s part to experiment with alternative methods of music distribution, like the decision to release “The Slip” for free in downloadable, non-DRM format.

For those unfamiliar with the game, Tap Tap Revenge resembles rhythm-based games like Dance Dance Revolution and Guitar Hero. Players tap glowing dots as they come down one of three neon-colored lines, trying to hit the dots in time with the music as they hit the bottom of the iPhone’s screen. The original version has been featured in Apple commercials, and it is highly likely that their endorsement will see more major artists following NIN’s lead, depending on the success of this most recent release.

Tap Tap Revenge: NIN not only features the band’s music, but also sports a custom red-and-black theme with all new graphics, and unlockable difficulty levels and tracks. You can get it in the App Store now for $4.99, or try the original version first for free.

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