This term is normally used to refer to the tradional synthesis model used by analog synthesizers in the 1970s. It is also known as subtractive synthesis. It involves oscillators, the outputs of which are mixed together and fed into a filter (where certain frequencies are subtracted) after which they are fed through an amplifier. The amplifier and filter are normally also driven by envelope generators....
Rogue
The Rogue, a "Miniaturized, cost-cutting successor" to the Moog Prodigy, is a 2-VCO,
monophonic synthesizer with a 2-1/2 octave, 32-note (F-C) keyboard. Both VCOs are
tunable to three octaves by a common switch. In addition, VCO2 is tunable via a knob to
anywhere between a half-step below to an octave above VCO1. There is also a single
switch that selects the waveform for both VCOs. A three position switch syncs VCO2 to
VCO1. It can be hard synced or contoured synced, where the amount that VCO2 is
synced to VCO1 is controlled by the envelope generator. The mixer section allows both
VCOs and the noise generator to be mixed together, with a slider controlling each level.
The mixer can be pushed to overdrive (distort) the waveforms. The filter section
features variable keyboard tracking controlled by a knob, and sliders for the cutoff
frequency, emphasis (resonance), and envelope amount. It also has "the pitch and mod
wheels up above the keyboard, not to the left of it, along with a fine tune knob and a
glide (portamento) knob." The Rogue has a single envelope generator for attack and
decay, that switches to activate the sustain mode. There is also a switch that selects
how the envelope affects the VCA. It can be set for either contour, keyed, or bypass
(which was a simple organ-style gate).