The analog synthesizer has one or more signal generators or Voltage Controlled Oscillators.
Sine Sawtooth Triangle Pulse-Width Square.
These waveforms can differ between instruments but generally they are all similar for the range of synthesizers now in use.When using the (VCO) a frequency above 300 cycles per second should be fine to hear some sound.The mixer section (VCA) is usually the last stage of the signal path but some newer synthesizers have included stereo delay before the output stage of their signal path. Many analog synthesizers have an output mixer (VCA) in which the signal waveform from the open attenuator of the mixer section goes towards the voltage controlled filter.
(VCF) called a Voltage controlled filter modifies signals
that pass sound harmonics from the audio (VCO) which allow us to hear the output from the keyboard.
These signals are attenuated along with the amplitude of a sawtooth wave should this attenuation increase increase or opened further it will let the signal pass through.When a synthesizer is patchable you can insert patch cords from an output into an input, ( if you insert an input to an input you will not get any sound).
Attenuators have a wide range and the amount of signal control they allow depends upon the operation range
the user gives to the signal.
Where a synthesizer is hard wired the filter and voltage controlled amplifier (VCA) will need to be opened to hear sound also a key or note will need to be pressed down on the keyboard to listen to the sound output. A drone or even a constant pitch can also be applied to the output of the (VCA) so the decay, sustain, and release sliders of the envelope generators may need to be applied to the ADSR section of any analog synthesizer.