Guitar Hero has been axed. Harmonix has stopped development on Rock Band and Dance Central. For the most part, it seems as though the music genre has contracted. However, one game has managed to drunkenly stumble into success: SingStar.

Sony's karaoke franchise has been a PlayStation mainstay since its introduction in 2004. However, the music platform has found new legs ever since Sony introduced a "free-to-play" version of the game. The base app includes no songs, but allows players to buy new songs online while still playing content from previous games.

According to DigitalSpy, SingStar has added 1.5 million new users since going free-to-play. Undoubtedly, most of those users are from Europe where the game is actually pinned to the PS3 XMB. American gamers will have to browse the PlayStation Store to download and install the app.

"It's nearly doubled our online userbase," Sony's Dave Raynard revealed during a Develop conference. The success of the app means that the franchise will stay digital going forward.

Raynard says that SingStar has about a six percent conversion rate, and like other free-to-play games, there are whales "who spend loads." Others will purchase "just a few songs." However, while the SingStore is regularly updated, the library is still quite lacking, especially when it comes to having newer songs.