Undivided. An incomposite interval is a large interval which appears as a melodic step or second in a scale, but which is a skip in other parts of the scale or in other related scales.
The Minor Third (augmented second) is an incomposite interval in the Black Key pentatonic, but a composite one in the diatonic or White key collection.
To illustrate Chalmers's example:
Black Key Pentatonic
m3 m3
|----| |----|
F# G# A# C# D# (F#)
The minor-3rds in this scale are incomposite.
White Key Diatonic
m3 m3
|-----| |------|
C D E F G A B (C) (D)
|-----| |--------|
m3 m3
The minor-3rds in this scale have other scale steps coming between them, and thus they are composite.
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