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A pentatonic scale is a musical scale with five pitches per octave in contrast to an heptatonic (seven note) scale such as the major scale. Pentatonic scales are very common and are found all over the world, including but not limited to Celtic folk music, Hungarian folk music, West African music, African-American spirituals, Jazz, American blues music and rock music, Sami joik singing, children's songs, the Greek traditional music and songs from Epirus, Northwest Greece and the music of Southern Albania, the tuning of the Ethiopian krar and the Indonesian gamelan, Indonesia Kulintang, melodies of Korea, Japan, China and Vietnam (including the folk music of these countries), the Afro-Caribbean tradition, Polish highlanders from the Tatra Mountains, and Western Classical composers such as French composer Claude Debussy.

Hemitonic and Anhemitonic

Ethnomusicology commonly classifies pentatonic scales as either hemitonic or anhemitonic. Hemitonic scales contain one or more semitones and anhemitonic scales do not contain semitones. For example, a hemitonic pentatonic scale common in some areas of North and West Africa contains flatted 2nd, 3rd, and 6th degrees (hence, if the scale begins in C, it will contain a D-flat, E-flat, and A-flat, plus a G-natural).

Major Pentatonic Scale

Anhemitonic pentatonic scales can be constructed in many ways. One construction takes five consecutive pitches from the circle of fifths; starting on C, these are C, G, D, A, and E. Transposing the pitches to fit into one octave rearranges the pitches into the major pentatonic scale: C, D, E, G, A, C. 

Another construction works backward: It omits two pitches from a diatonic scale. If we were to begin with a C major scale, for example, we might omit the fourth and the seventh scale degrees, F and B. The remaining notes, C, D, E, G, and A, are transpositionally equivalent to the black keys on a piano keyboard: G-flat, A-flat, B-flat, D-flat, and E-flat.

We can also omit the third and seventh degrees of the C major scale to obtain the notes another transpositionally equivalent anhemitonic pentatonic scale: {F,G,A,C,D}. If we omit the first and fourth degrees of the C major scale we have a third anhemitonic pentatonic scale: {G,A,B,D,E}.

Minor Pentatonic Scale

Although various hemitonic pentatonic scales might be called minor, the term is most commonly applied to the relative minor pentatonic derived from the major pentatonic, using scale tones 1, 3, 4, 5, and 7 of the natural minor scale. Thus C minor pentatonic would be C, E-flat, F, G, B-flat. The A minor pentatonic, the relative minor of C, would be the same tones as C major pentatonic, starting on A, giving A, C, D, E, G. This minor pentatonic contains all three tones of an A minor triad.