To create a drupal module compatible with Drupal 6.x for logged in users to upload audio files.

Uploaded audio files need to be displayed on the user's profile as well as in various views on other pages, eg. "recently uploaded music", "top listened to music".

Can you also integrate with Ubercart so that users can sell audio?

For this option users upload single "song" or "album of songs" , set the price or "free", enter title, genre, isrc code, etc.
If audio is for sale or for free download, their must be a link to "buy" or "download" when audio displays on the profile.