Moog’s Theremini has a pitch control knob that, when set at 100, makes it impossible for the musician to play a wrong note. Players can turn the knob all the way down to zero for gradually decreasing levels of pitch assistance. The Theremini also has a built-in tuner that shows players how close to perfect each note is in real time, a useful feature that could help beginners learn to master the unusual instrument.
via Laughing Squid
