This is an interesting find. While assessing 1/4" acetate tapes from the 1950's, I came across this oddity. At first glance, it appears to be a weird 3 track recording.
After playing back through a full track mono head (and sitting in front of the machine in total confusion for a few minutes) I was able to determine that the tape originally had another song recorded at high level in full track mono, and then a new, lower level stereo song was recorded on top of it.
The skinny "middle track" is actually the leftover material from the mono song that wasn't able to be erased due to the NAB head gap of the stereo head. Since the newer song was recorded and played back with a stereo head, no one noticed that the other song was there. Mystery solved!
#unitedarchiving #unitedrecording #ampex #scotchtape #monorecording #stereorecording #audiopreservation #audiodetective #audioengineer #magneticviewersaretheshit