I found a way to find the sources of Scratch sounds (for 1.4 at least), and listen to the tracks in stereo.
Install 1.4, then go to wherever you installed Scratch 1.4 (for me it was C:\Program Files (x86)\Scratch).
Go to the Media folder, then Sounds. Now if you go into a folder in there you will find a bunch of sounds.
Some of them contain contributing artists or an album.
For example, I found that “Techno” was made by gloob(ic) in the album “mass ave sessions” called “gryrow”.
Here's the source: http://www.gloobic.com/mass%20ave%20sessions/02_gryrow.mp3
Cool, right?

neato

Is there a newer link? The link doesn't work for me.