Heptatonic scale
A
heptatonic scale is a musical scale with seven pitches per octave. Among the most famous of these are the
major scale, C D E F G A B C; the
melodic minor scale, C D E♭ F G A B C ascending, C B♭ A♭ G F E♭ D C descending; the
harmonic minor scale, C D E♭ F G A♭ B C; and a scale variously known as the
Byzantine,
Hungarian,
gypsy, or
Egyptian scale, C D E♭ F♯ G A♭ B C. South Indian classical theory postulates seventy-two
melakarta, seven-tone scale types, whereas Hindustani classical music postulates twelve or ten seven-tone scale types collectively called
thaat. Most heptatonic scales of Western, Hungarian, Arabian, Greek, and Indian musics can be analyzed as juxtaposition of tetrachords. All heptatonic scales have all intervals present in their Interval vector analysis, and thus all heptatonic scales are both hemitonic and tritonic. There is a special affinity for heptatonic scales in the Western Key signature system.