Pleiades BD139 Oscillator Schematic

At your risk. Take all safety precautions. A suitable fuse must be in series with any battery.

Another variable resistor can be added in the feedback path instead of the wire link.

This schematic naturally derived from the Pleiades 2N3053 single transistor audio power amplifier operating in class A (electrons flowing all the time). 

Most of this plus the original schematic (above) is derived from the electronic construction  game with springs Polycyclomatic 1002. Here is how it looks like:

https://www.radioerasitexnisam.gr/articles/15-%CF%80%CE%BF%CE%BB%CF%85%CE%BA%CF%85%CE%BA%CE%BB%CF%89%CE%BC%CE%B1%CF%84%CE%B9%CF%83%CF%84%CE%AE%CF%82-%CF%84%CE%BF-%CF%80%CE%B1%CE%B9%CF%87%CE%BD%CE%AF%CE%B4%CE%B9-%CF%84%CF%89%CE%BD-70s

Thank to a discussion on the beach with John and his Xenophon, both studying engineering there was encouragement to just convert one of the Pleiades single transistor prototypes. In just a few seconds a nice oscillator came up. Wago connectors made the modification possible so quickly. The 12V battery powered oscillator was feeding a Philips 8 in woofer. By adjusting the 2 variable resistors a bass sound repeated in tempo was created. The tempo can be changed by touching the cone of the speaker for current unknown reason. So there is much more flexibility as the pitch can also be affected.

2 Shure Unidyne B microphones, one behind the other at 24in were used to record in stereo the oscillator together with a glockenspiel. The result has some kind of magic from the natural reverberation of the glockenspiel together with the antithesis of the electron generated bass with harmonics sound. It was recorded on SONY TC-D5M.