image courtesy of Kevin Lightner

The Pro-One is a monophonic, two oscillator synthesizer with a 3 octave, 37-note (C-C), keyboard. VCO1 is switchable between sawtooth and pulse waveforms (either or both) and can be synced to VCO2. (VCO1 and VCO2 are actually called "VCOA" and "VCOB".) VCO2 is switchable between sawtooth, triangle, or pulse waveforms (any or all) and has a switch to disable keyboard control. It can act as an LFO. The LFO can output a sawtooth, triangle or a square waveform and can be set to retrigger on key press.

The Pro-One has two envelope generators (ADSR), one for the VCF and one for the VCA. The VCF is 4-pole lowpass and will self-oscillate. The VCF has controls for frequency cutoff, resonance, envelope modulation amount, and keyboard follow amount. There is a filter input control which is a mixer for VCO1, VCO2, and noise or external audio in. The available modulation sources are Filter Envelope, VCO2, or LFO. These sources can modulate VCO1 frequency, VCO1 pulse width, VCO2 frequency, VCO2 pulse width, or the filter. The Pro-One has a 40-note dual sequencer with a volatile memory (the sequence is lost when you turn the instrument off) and an arpeggiator.

The keyboard is digitally scanned. The glide can be switched so it only glides when you press a key before releasing the previous key. There are controls wheels to the left of the keyboard which are pitch bend and modulation amount. There are two modulation busses, one is direct (non-attenuated) and the other can be attenuated by the mod wheel.

The back panel has audio out, external audio in, and CV/gate in and out. External audio in can also be used to generate a gate signal.