Though I think Stu's right on the money, a few more clouds are hanging over my brain. grin

Here's more to think about from a poster on another thread:


Here are several libraries that work on a copyright buyout basis with composers..

Megatrax
APM
KPM
Killer Tracks
Extreme
615
Manhattan Production Music
Opus 1 (sometimes)
Firstcom
Master Source

Things would get super complicated if one of these libraries wanted to buy a track that you copyrighted in a folio of works. The legal fees trying to unravel the situation would probably eclipse the phat $1000/track budget of these libraries..

Most of the time the libraries pay upfront for composers to make custom music, but they also actively buy copyrights of already composed material from time to time.