The Schaller Banjo B4 D-Tuner is a tuning machine with inbuilt stops, that allows banjo players to preset two different tunings while playing. They are delivered as a set with two different string axes. The pitch of the string can be changed by half a tone on the thin post, and by a whole tone on the thick post. By means of knurled screws, the up- or down-tuned notes can be fixed to the tuning machines housing.