Inmusic theory, aneutral interval in24 TET (including extensions), (but also known as asubmajor interval, or as asuperminor interval, inJust Intonation), is aninterval that is neithermajor nor minor, but is, instead, in-between them.

In12 TET, these intervals are aquarter tone sharper than minor intervals and a quarter tone flatter than major intervals. For example, theminor third is tuned at 300¢, while themajor third is a semitone (100¢) sharper (400¢), and so theneutral third lies between them at 350¢.

A neutral intervalinverts to another neutral interval.

In just intonation, as well as in tunings such as31-ET,41-ET, or72-ET, which more closely approximate it with more of them, such intervals can be closer together.

intervals	minor	neutral	major
seconds	D♭	D	D♮
thirds	E♭	E	E♮
sixths	A♭	A	A♮
sevenths	B♭	B	B♮

Aneutral second ormedium second is an interval wider than aminor second and narrower than amajor second. Three distinct intervals may be termed neutral seconds:

• The intermediate neutral second, called thelesser undecimal neutral secondplay^ⓘ, has a ratio between the higher-frequency tone to the lower-frequency tone of 12:11 and is about 150.64 cents wide, while the larger one,
• thegreater undecimal neutral secondplay^ⓘ, has a ratio of 11:10 between the two tones and is about 165.00 cents wide. The lesser undecimal neutral second may be derived from theharmonic series as the interval between theeleventh and twelfth harmonics. The greater undecimal neutral second may be derived from theharmonic series as the interval between the tenth and eleventh harmonics.
• Anequal-tempered neutral secondplay^ⓘ is characterized by a difference in 150cents between the two tones, a hair smaller than a ratio of frequencies between the two tones of 12:11, and exactly half of an equal-tempered minor third.

The equal-tempered neutral is found in some traditionalArabic music (see alsoArab tone system). Because the equal tempered neutral second is essentially a semitone (minor second) plus a quarter-tone, they may be consideredthree-quarter tones in thequarter tone scale.

Approximations to the 12:11 and 11:10 neutral seconds can be found in a number of equally tempered tuning systems. 11:10 is very closely matched by22-ET, whereas 12:11 is matched by24-ET,31-ET and41-ET.72-ET matches both intervals closely and is also the smallest widely used equal temperament that uniquely matches both intervals. Tuning systems that temper out thecomma of 121:120 do not distinguish between the two intervals.17-ET has a neutral second between 12:11 and 13:12, and a neutral third between 16:13 and 11:9.

Aneutral seventh is a musical interval wider than aminor seventhplay^ⓘ but narrower than amajor seventhplay^ⓘ. Four distinct intervals may be termed neutral sevenths:

• Aseptimal neutral seventhplay^ⓘ has a ratio of 64:35 or about 1045 cents.
• The justundecimal neutral seventh has a ratio of 11:6 between thefrequencies of the two tones,^[3] or about 1049 centsplay^ⓘ. Alternately, 13:7^[3] or about 1071.7 centsplay^ⓘ.
• Atridecimal neutral seventhplay^ⓘ has a ratio of 24:13 between thefrequencies of the two tones, or about 1061 cents. This is the largest neutral seventh, and occurs infrequently in music, as little music utilizes the 13thharmonic.
• Anequal-tempered neutral seventhplay^ⓘ is characterized by a difference in 1050cents between the two tones, a hair larger than the 11:6 ratio, and exactly half of an equal-tempered major thirteenth (octave plus major sixth).

These intervals are all within about 12 cents of each other and are difficult for most people to distinguish.

A neutral seventh can be formed by stacking aneutral third together with aperfect fifth. Based on its positioning in the harmonic series, the undecimal neutral seventh implies aroot one perfect fifth below the lower of the two notes.

• Major fourth and minor fifth
• Subminor and supermajor
• List of pitch intervals
• Microtonal music

• Neutral intervals
• Quarter tones

• Pages using the Phonos extension
• Articles with short description
• Short description matches Wikidata