I agree that it sounds unlikely, hence the incredulity factor (?!?) in the header. However, I admit being facinated, in a morbid sort of way.
Each individual channel/track seems to come "down a chute" about 1 1/2 octaves wide, with each channel/track/chute centered on a different frequency.
It is not only weird, it is kind of creepy!
Sorry to say, I sort of lost track of the quality of the performance once I got wind of the "track" thing; but your explanation is interesting enough that I will indeed watch for the "same" performance, and then I will compare copies.
Also, interesting note that DGG started messing with the digital in the early 70s! IMO, they were already a mixed bag by the mid/late 60s.