Heptatonic scale

A heptatonic scale is a musical scale that has seven pitches, or tones, per octave. Examples include:

• the diatonic scale; e.g., in C major: C D E F G A B C—and in the relative minor, A minor, natural minor: A B C D E F G A
• the melodic minor scale, A B C D E F♯G♯A ascending, A G F E D C B A descending
• the harmonic minor scale, A B C D E F G♯A
• the harmonic major scale, C D E F G A♭B C.

Indian classical theory postulates seventy-two seven-tone scale types, collectively called melakarta or thaat, whereas others postulate twelve or ten (depending on the theorist) seven-tone scale types.

Several heptatonic scales in Western, Roman, Spanish, Hungarian, and Greek music can be analyzed as juxtapositions of tetrachords.^[1] All heptatonic scales have all intervals present in their interval vector analysis,^[2] and thus all heptatonic scales are both hemitonic and tritonic. There is a special affinity for heptatonic scales in the Western key signature system.