JACK autotuner

 AT1 is an 'autotuner', normally used to correct the pitch of a voice
 singing (slightly) out of tune. Compared to 'Autotalent' it provides
 an improved pitch estimation algorithm, and much cleaner resampling.
 .
 AT1 does not include formant correction, so it should be used to
 correct small errors only and not to really transpose a song. The
 'expected' pitch can be controlled by Midi (via Jack only), or be a
 fixed set of notes. AT1 can probably be used on some instruments as
 well, but is primarily designed to cover the vocal range. It's also
 usable as a quick and dirty guitar tuner.