Apple's iPhone and App Store have spawned a veritable industry of mobile application developers. And while many startup companies are panning for gold, Tapulous, the developer behind Tap Tap Revenge, has a record of consistent success.

Tap Tap Revenge was the App Store's most popular game of 2008 with more than 11 million downloads, according to company data. The rhythm game uses the touch-screen interface of the iPhone and iPod Touch to offer a music experience similar to the highly successful "Rock Band" and "Guitar Hero" franchises.

Thanks to a new iPhone software upgrade, Tapulous will now be able to sell new songs for the game for 50 cents each, in much the way "Rock Band" offers downloadable content. Universal Music Group is the first label to license its music to the company for that purpose and will release artist-specific versions of Tap Tap Revenge for $5 each, starting with one based on Lady GaGa. The deal follows the success of earlier artist-branded versions of the game from Nine Inch nails, Coldplay and Dave Matthews Band.

In a sign of Tapulous' growing ambitions, Universal will also work with the app maker to develop new music game titles for the iPhone.

Billboard caught up with Tapulous co-founder/CEO Bart Decrem to hear more about the company's plans, how the iPhone's software affects app developers and what investors think of the market.

Was creating artist-specific Tap Tap Revenge games your goal from the start?

I like to say we're the accidental gaming company. On launch day, there were three songs in the game that were done by a friend of the company and some indie bands. And it flew right to No. 1. Very quickly, independent artists approached us to get their music in front of gamers. We've built a strategy around making the game a real brand and a real community. These artist editions of the game are an important part of that strategy. It's not just that fans want to play to music they love, they want to have an experience that's about their band. It's not just about playing Lady GaGa songs in Tap Tap Revenge. You want to have a Lady GaGa experience. So that's where these special editions of the game fit in.

How is developing an artist-specific game different from the core Tap Tap Revenge title?

The special editions have more of a concept of levels and unlocking songs at each level. Each level gets harder, so we try to be thoughtful about how we pick the songs so there's a sense of work. When you listen to an album, it's not just 10 songs thrown together; there's a sense of a narrative there. We're trying to do the same thing with these editions.

Will the number and frequency of artist-based games increase with the Universal deal?

Click here for the full Q&A, which includes Decrem's thoughts on the possibility of "Rock Band" or "Guitar Hero" developing a version of their games for the iPhone, today's funding environment and more.