More often than not, the MIDI velocity value serves its namesake purpose, directly controlling the amplitude of a sound to simulate the fluctuating dynamics of striking an acoustic instrument at different "velocity". That same variable-strike effect is sometimes better achieved by controlling less obvious parameters, like modulating the frequency of a filter or the release time of an envelope for dampening on "softer" hits.

These specific cases really only hint at the possibilities of what MIDI note velocity can control - indeed, it might be better to eschew the name "velocity" entirely and think about it in its more generally applicable way. After all, velocity is just an arbitrary number from 0-127 tied to each MIDI note, and with a little bit of experimentation and setup you can apply it to all sorts of interesting functions that have nothing to do with velocity in the traditional sense. In this article, we'll explore velocity as an versatile modulation source.