Honestly in my view it's better to be discreet about legal issues. However there is nothing confidential involved and all patent applications are searchable on Google.
Harmonix, the creator of Rock Band/Guitar Hero, as of 2009 is attempting to patent a process that is broad enough to cover Audiosurf and similar games that implement gameplay based on analyzed features of the user's music.
Note that Harmonix to my knowledge has not released any games with this feature. However a company does not have to in order to patent something. Look up "patent trolls."
Here's the app:
http://www.google.com/patents?id=8HTHAAAAEBAJ&zoom=4&dq=%22in%20the%20groove%22%20%22dance%20dance%22&pg=PA1#v=onepage&q=%22in%20the%20groove%22%20%22dance%20dance%22&f=false1) Access Musical Content
2) Analyze Musical Content to Determine Musical Events
3) Determine a Property Associated with the Identified Event
4) Create Game Event Synchronized to the Identified Event and Reflective of the Determined Property
It does not matter "how" specifically Audiosurf does this. Harmonix is eyeing a patent on the "idea" of doing this.
Does this sound looney? Well they may very well be successful. You might want to write a letter to Congress to reform our deeply flawed patent system and the way it applies to software. Look at this article:
http://arstechnica.com/gaming/news/2008/03/patents-on-video-game-mechanics-may-strangle-innovation.ars.
I am not a patent specialist. I do, however, know enough about patent law to suggest that Dylan get in touch with a specialist.
There are legal challenges he could bring. HOWEVER this situation is not strategically straightforward. Legal challenges cost money. Certain forms of challenge have different long-term implications from others. If Harmonix tries to bully "competitors" around, they will still need to hire lawyers to defend themselves.
Which is why he needs to be advised by somebody who knows what they are talking about. Any response to this must be made with someone with experience and knowledge of the field to be able to look ahead several steps at the implications of different actions. Trying to sort this out otherwise is like, as I told blue_h3x, trying to understand and diagnose a circuit board with no prior EE experience. This knowledge and intuition can't be found by Googling for a few hours about patent law - it needs to be accumulated over actual experience litigating cases, knowing how courts react to certain arguments, and working with these situations.