for Song Surgeon users, it's youtube sniffer will allow you to download these backing tracks.
Just for a test, I downloaded the Blues in F track - it is more than 23 minutes long!!
It's a .wav file, so it's pretty big too.
Tom
Edit - I downloaded a bunch of these tracks. Most of them are very long. 3 tunes = a one hour set!
I saw a couple of the jazz ones that were over 25 minutes. Shortest one I saw was over 5 minutes.These will be great for some extended improv practice time, or for trying out different ideas without stopping and restarting a backing track.