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....
CS-05
The CS-05 is a single oscillator monophonic synthesizer with a 3 octave, 37-note (C-C)
keyboard. the voice architecture consists of a single VCO, a VCF, a LFO, and a simple
envelope generator. The VCO (Voltage Controlled Oscillator) has sliders controlling the level of
it's two waveforms, sawtooth, and pulse. The pulse width can be modulated by the LFO (Low
Frequency Oscillator). The LFO features a sample-and-hold setting and can modulate up into
the audio range for FM sounds. There is an input and a trigger circuit which allows you to trigger
a sound via an external audio signal.