The General CV is a combination of a powerful General MIDI synthesizer, a multi-channel CV-to-MIDI converter, and a host processor capable of generating huge amounts of MIDI data, either in response to control voltages (CVs) or entirely algorithmically.
The module's software provides a layer of control over the synthesizer allowing you to create sounds far beyond the familiar (cheesy, even) sounds of General MIDI with which you might be familiar. From making the synth behave like a VCO, to creating complex chords and textures, and even to abusing drum sounds into pitched audio sources, the General CV will add a rich selection of fresh sounds to your modular synth.
(Though it will also play any MIDI files of 80's pop tunes that you might happen to download from the web.)
The General CV is a 12HP Eurorack module.