A modular synthesizer is one where the structure of the synthesizer isn't fixed. There are a variety of modules available which can be plugged into each other. Tradionally these modules were physical boxes, but they can now be emulated with software and patched with on-screen cables....
Pro-One
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. VCO2 is switchable
between sawtooth, triangle, or pulse waveforms (any or all) and has a switch to disable keyboard control. The LFO
can output a sawtooth, triangle or a pulse waveform. The Pro-One has a single envelope generator (ADSR). The
VCF has controls for frequency cutoff, resonance, envelope modulation amount, and keyboard follow amount. The
VCA is controlled by the ADSR. 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.