Virtuemart 2 - creating an option for a single or product that removes carriage

[OGBoardman]

Hi, i'm currently selling albums on my site. I have set it up so that the carriage is automatically added for the shipment of CD's, however I would like to give my customers the option of removing the carriage in the cart or checkout and just have the mp3 download. How can I do this?

I already have the downloadable product in place.

Thanks in advance