via Nyle Steiner:
An electronic sound composition is made entirely of sounds produced using zinc negetive resistance audio oscillator circuits. No vacuum tubes or transistors were used to generate the sounds.
Several tracks of the zinc oscillator sounds were recorded one at a time. Some of the sounds were enhanced with the addition of reverb.
The morse code parts were sent in real time by manually keying a J-38 straight key. Yes, I can send that fast with a straight key by using a somewhat unusual technique that I developed.