In order to play AAC-encoded songs (typical file extension: .m4a) you will need to install Quicktime into the bottle containing Audiosurf and then manually copy one file*:
1.) Download the windows version of quicktime to a convenient location.
2.) Install the downloaded package by opening the Bottle Manager, selecting the Audiosurf bottle, switching to the control panel tab and starting the "Software" application. Click on the "Install" button in the software dialog and pick the package downloaded in step 1. NB: installing the package into Steam/Audiosurf bottle using the Crossover installer fails (for me, tm).
{*3.) Open the bottle in the finder and navigate to "Program Files/Quicktime/QTSystem", copy the QTFC.dll and paste it into the "windows/system32" directory of the bottle.}
(* Step 3 is un-needed on Crossover 13.0.1. Just install Quicktime 7 from Install Software Menu)
A library override seems to be unnecessary.
