Treble shift

A mechanical device on an accordion that directs air from the bellows through additional reeds to create a different tone quality of the melody notes. There are typically four sets of treble shifts, one set tuned in unison, a second set tuned one octave higher, a third tuned one octave lower, and the fourth set, the tremulant, tuned slightly higher than unison. A universal system of labels has been given to these treble shifts for the composer to designate specific sounds.Table of Treble Shifts and LabelsUnison onlyUnison & Lower OctaveLower Octave onlyUnison & Higher OctaveHigher Octave onlyUnison & TremulantHigher Octave & Lower OctaveUnison, Higher Octave & Lower OctaveUnison, Higher Octave & TremulantUnison, Lower Octave & TremulantMaster (all sets)