For the location for the download, you should organize them in a folder for each type, and based on what format the user clicks then you could pull the requested file from that specific folder.
linking the track and albums into multiple categories requires an additional table to join the product table and the categories table. so you will need a product table and then a categories table and then a third table (product-categories table) which will have the category id and the product id to link the two tables.
for downloading albums, i think you will need to add it as a separate product and you will need a way in the database to indicate that.
as far as the database structure, this link have a database you could use as a starting point:
which i think will be sufficient enough for your purposes but you are going to need to add the options tables and the tables needed for the categories.