A monophonic analog synthesizer with a 37-note keyboard. Produced between 1980 and 1984. Considered to be Sequential Circuits' counterpart to Roland SH-101.

The Pro-One has two VCOs per voice. VCO1 is switchable between sawtooth and pulse waveforms and cand be synced to VCO2. VCO2 features sawtooth, triangle and pulse waveforms and a noise generator. It also has a switch to disable keyboard control.

There's a sawtooth/triangle/pulse LFO and a single ADSR envelope generator which controls the VCA.
The VCF is the same CEM 3320 chip used since revision 3 in the Prophet-5. It has controls for frequency cutoff, resonance, envelope modulation and keyboard follow.

Available modulation sources are filter envelope, VCO2 or the LFO. They can modulate VCO1/VCO2 frequency, VCO1/VCO2 pulse width or the filter.

The Pro-One includes a 40-note dual sequencer with volatile memory. This means the sequences are lost when the power is turned off. An arpeggiator is also featured.

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