OK, how do I do this;

I have a product that is a 2 CD set, part1 and part2, but it is one item and is sold as such.

I want to have it as a downloadable MP3 but I want the customer to be able to select one item and then
be able to download both files at checkout.

Right now I can only see a way to have one downloadable file associated with an attribute as an option,
but not a way to have multiple files on one 'option'.

I could put both files into a single zip file but the problem is it would be far too large to be practical.

Thanks :)