Yes, Audiosurf. But Hexcells creator Matthew Brown Games says his next game approaches a similar idea in a different way. Where Audiosurf was about the music, Brown intends Sound Shift to be about the racing. That your tracks come from the music you're playing is a bonus.
But what's most striking here at a very early stage is the emphasis on design. Take a look at this early footage:
The most obvious details are the lovely use of graphic equalisers both below the track and in the centre of it. Beyond that, it's the finesse that struck me. While track times and laps take up a fairly typical position top right, they're clean, neat and well placed. And the speed you're travelling is written on the back of your mouse-like vehicle. Clutter is reduced to a minimum. But what you won't see much of in that video is the way the game reacts to touching the sides. Bump a wall and all the written information on screen tears as if on an old television going out of tune, while the music itself reacts, turning tinny like it's coming through poor headphones. Having the interface react, rather than attempting to portray that through the vehicle (or god forbid, shaking the screen), becomes a really interesting way of feeding back, and puts a bigger emphasis on wanting to succeed.
It's hard to justify that with words, but I've had a play of a very early prototype of the game (just a single pre-built track at this stage), and it's enormously effective. I can also attest that if that's Brown playing the game himself in the video, then he is some sort of racing guru, because trust me - it's not that easy. With an emphasis on speed, this isn't a game where you can just put your foot down and screech around the corners. You're almost immediately going over 300kph, and that's not a realistic turning speed. Acceleration needs to be carefully managed.
Clearly this is very early days, and the prototype doesn't yet offer the game's key feature: building tracks according to the music you're playing. But the dude made Hexcells, so I'm plugging whatever he's working on next. You can keep up to date with the project on its TigSource page, and hopefully soon on the game's own page.