Dodo MIDI is a free voice to MIDI plugin that detects incoming audio, which can be voice or musical instruments, and translates it into MIDI that you can use to control any MIDI synth.
Here’s what the developer has to say about it:
“What sets it apart from all the other audio to MIDI software packages available, is that it really works incredibly well and is extremely useful as a live musical instrument! For the first time, you can play (almost) any synthesizer or sampler just by using your voice, with imperceptible latency, and exceedingly accurate control over legato, slides and articulation.”
The above video demonstrates how to get started with the plugin. The following video demonstrates how to set it up to control a MIDI instrument:
Dodo MIDI is available now as a free download for both macOS & Windows.