Neutral interval

Three distinct intervals may be termed neutral seconds: The equal-tempered neutral is found in some traditional Arabic music (see also Arab tone system).

Because the equal tempered neutral second is essentially a semitone (minor second) plus a quarter-tone, they may be considered three-quarter tones in the quarter tone scale.

Approximations to the 12:11 and 11:10 neutral seconds can be found in a number of equally tempered tuning systems.

Tuning systems that temper out the comma of 121:120 do not distinguish between the two intervals.

Based on its positioning in the harmonic series, the undecimal neutral seventh implies a root one perfect fifth below the lower of the two notes.