We did these back in high school. If I remember right, we used a stereo tape deck, probably a Wollensak, with music on one channel and a tone to trip the slide projector on the other channel. We matched appropriate images of the times (war protests and such) with Simon & Garfunkel's Sounds of Silence. Actually made a pretty decent impression, though we certainly weren't sophisticated artists at the time. The closest thing we had to a computer back in '72 was a floor standing programmable HP (I think) calculating machine.