Digital Download

Hi All,
I am creating a website for a friend who sings at corporate events etc.

WordPress has covered all the options that we need.

However I am now looking to encorperate a digital download module where her tracks can be uploaded and the users can search and pay for them, and then be able to download them.

I would be greatful of any advice provided even if it does not fit the bill completly.

Regards
Nitro