So I'm a keys player, when I compose I choose a key and write chord progressions, etc. Whenever I watch videos of tutorials/performances on modular unit I can never find out how the aspects such as key signature/melodies and other such 'gestures' are inputted. Does that make sense?

I'm looking into MIDI to CV converters for playing a keyboard - but how would I sequence/'capture' what I play in? Or what are the other methods?

I hope this makes sense, I've just been unable to find out how so far.