Adjustment in tuning (i.e. ‘tempering’) of mus. intervals away from ‘natural’ scale so that such pairs of notes as B♯ and C, or C♯ and D♭, are combined instead of being treated individually. This leaves neither note accurate but sufficiently so for the ear to accept it. In kbd. instr. this avoids unmanageable number of finger‐keys. The pf., organ, and other fixed‐pitch modern instr., are tuned to equal temperament, in which each semitone is made an equal interval, making it easy to play in any key and to modulate. Before equal temperament (which was introduced for pfs. in Eng. in 1846 and for organs a little later), the commonest system was mean‐tone temperament, which left certain keys tolerable, others less so, and some unusable. The untempered scale is known as just intonation. Instr. such as the vn. family can have no system of temperament, the player determining the pitch and checking it by ear. Some 20th‐cent. composers have restored 12‐note scale to just intonation. Others have used microtonal scales in just relationship. Still more have used ‘prepared’ instr. producing unexpected pitches, or elec. systems, or computers.