Buchla 258t

Dual Oscillator Model 258t

Two independent voltage-controlled oscillators.
Each has one processing input, a frequency modulation input and a 1V/oct input. Waveshapes, as well as frequency, can be voltage controlled. Model 258 oscillators feature low sine wave harmonic content, negligible settling error, and high short and long-term stability, even with rapidly changing ambient temperatures.

TRIMMERS:
There are three trimmers for each oscillator on the back of the module:
1V/oct is the octave tracking trimmer and is set at the factory using high precision instruments.
SHAPE is the trimmer that set the sine wave, for the lower harmonic content of the sine wave.
VC WAVE SHAPE sets the response of the waveshaper to the incoming control voltage. Both SHAPE and VC WAVE SHAPE trimmers are used to adjust the sine wave purity.

https://tiptopaudio.com/buchla/