Highly doubtful for audiogames. Its an entirely different matter though for day-to-day use; i'd recommend getting an I5 at least.

It can actually matter quite a bit. the more complex the game, the more it matters. For example when you're playing blast chamber it won't matter much but if you play a large map with many units in tactical battle and you have a slow processor, the battle report will take a while to generate.
If you want to play more complex games, I would also go for an i5. Also take a look at the number of cores and the speed (ghz) of the processor. a dual core processor at 2.5 ghz should be enough.

Overall I agree, audio games have very, very low system requirements compared to mainstream games. No doubt part of this is the high demand placed on the system from graphics not being needed in audio games.

For performance within Windows any quad core I5 would do great but don't worry too much about the GHz value, also try not to get the unlocked "K" model of the processor unless you plan to overclock because you lose the turbo boost function. Other than that cram in at least 4GB memory and the more the better, and an SSD really is fantastic for making your system start and shutdown faster but depending on your storage requirements you might need to back that up with a normal spinning hard drive.