An electronic circuit that analyzes the pitch of an input signal, and produces a control signal that represents the pitch (usually either a control voltage or a MIDI message). A pitch converter (coupled with an envelope follower) allows conventional instruments and human voices to be used to control synthesizers, as an alternative to a keyboard. However, accurate pitch conversion is a difficult task, and nearly all pitch converters suffer from mis-tracking to some extent, which is why they have not become particularly popular as a means of playing a synth.