I discovered something interesting this weekend at my mate's housewarming. He has a large Hammond style organ left over from the previous owners of the house, and when I had a look at it I noticed that it uses a continuous loop tape cartridge to store digital data (probably in a format similar to MIDI). Anyway, I just had to scan the tape and submit it - looking at the section on Playtape, it looks like an application of that technology. It seems to be a 4 mono track digital cart with sensing foil, and seems to use Chrome tape. That's about all I know. 

All I know about it is the organ is made by GEM, and the cartridge scanned dates from around 1983 (the copyright on the arrangement of the songs in the song booklet that comes with the cart says 1983 anyway). The deck on the organ (as pictured in the booklet scan) also records, and my mate has a blank tape as well.