I do have every one of these you linked to, although you did force me to
go downstairs to double check that I DO have the National Lampoon disc
-- I do, with the cover and inserts all in mint condition.  I've got
about two shelf-feet of demo and test records.  The Bel Canto demo is
the first pre-recorded stereo tape I bought, so I had ignored the disc
version for several decades -- until I found out it was multi-colored! 
I then quickly found myself a copy.  

Mike Biel  [log in to unmask]

-------- Original Message --------
Subject: [ARSCLIST] some early stereo demos
From: Tom Fine <[log in to unmask]>
Date: Wed, September 26, 2012 5:58 pm
To: [log in to unmask]

Here's some YouTube fun for the evening:
check out the funky colored vinyl!
hey camera dude, plug the line outs into your camera!

and then there's this:

-- Tom Fine