The oscillators, filter, modulators, and other parts are connected in the most useful ways for producing and modifying electronic signals that result in sounds. Unlike on a modular synthesizer, many connections between the Subsequent 37’s various parts are hardwired, meaning that it is not possible to change the routing of the pathways that connect them.
The electrical signals within a synthesizer are either audio signals or control signals, depending on the pathway they follow. Typically, an audio signal begins with an oscillator and passes through the filter on its way to the audio output. Control signals are used to change things, like the pitch, timbre, waveshape, or loudness of an audio signal.
Any time a signal controls something, no matter whether it’s controlling an audio signal or another control signal, we say that it modulates it. In synth-speak, you could say that a steering wheel modulates a car’s direction and the accelerator pedal modulates its speed. When you play the Subsequent 37’s keyboard, the key you press modulates the instrument’s pitch. You can modulate filter cutoff by turning a knob manually, or you can apply a control signal from a low-frequency oscillator or envelope to modulate it electronically. It’s worth noting that a control destination can be modulated by more than one control source.
The diagram below illustrates how the Subsequent 37 generates sound. It shows the flow of audio signals, represented by solid lines, and control signals, represented by dotted lines.