Thanks for the explanation Charley, that's about what I expected a "minus one" mix to be, but I wasn't entirely sure. It's definitely an approach that most musicians don't consider.

Here's another product to consider that is almost unheard of in musician circles - several years back the drummer from Aerosmith put together a collection of all of his drum beats and sold them for a certain price. If you paid that price you could have 100% use of them in your own material. This was partly as a response to having his drum beats being illegally used in other people's music anyway, so he gave them the "legal" option at a fair value and started to benefit from the practice.

I think many musicians are too attached to their music to consider this, and to be perfectly honest - in order for a product like this to truly take off you'd have to have a pretty strong audience that really likes your material and are also creative themselves. If you happened to discover that a large segment of your audience are professional musicians themselves this might be something that works for you.