just a bit of related fluff on the hidden marvels of the Involve wonderbox!
last Christmas i stumbled upon a way of wiping out all lead vocals from a Quad track, post-decoding thru the Surround Master vn.1 (the Minnie Riperton track "Reasons" in SQ) i can't recall how right now
but by a wee bit of fiddle-diddle-diddling i was able to take her vocals out of the whole Quad mix and put the 4 channels back together to create a nifty 2-ch backing track! i also managed (somehow!) to do a 4-ch Quad instrumental track but with Mono Rears..
wah wah wah wah wah! the reasons for doing it are buried in deep places.. but it was pretty cool (i thought!) i did the same with a Janis Ian track from SQ LP through the Surround Master (to similarly "ooh! ahh!" effect!) so it wasn't just a one-off.. anyway here's a sample clip of a 'no-Minnie Minnie' track (for reference purposes only!)
https://drive.google.com/file/d/11knCx7QRD7SlYrBVw6UGKMAU2USjZtOo/view?usp=drivesdk