Major and Minor Pentatonic Scales

Start with a major scale: seven notes, two of which sit a half step away from their neighbors, scale degree 4 (a half step above 3) and scale degree 7 (a half step below 1). Those two half steps also combine to form the scale's tritone, the unstable interval between 4 and 7. Pull out degrees 4 and 7 entirely and you are left with five notes, all a whole step or a minor third apart from each other. No half steps, no tritone, no pull toward resolution. That is pentatonic: open, stable, impossible to make sound clashing no matter what order you play the notes in.

This is exactly why the black keys of a piano form a pentatonic scale. Play only F-sharp, G-sharp, A-sharp, C-sharp, D-sharp in any order and nothing clashes, because that set of five notes has no half-step relationships built in. Minor pentatonic works the same way from the minor side: take a natural minor scale and drop scale degrees 2 and 6, again removing the two notes responsible for half steps and tension, leaving five stable notes.

Pentatonic scales connect directly to the major and minor scales just covered, since you build them by subtracting specific degrees rather than starting fresh. They also set up timbre and texture: because pentatonic melodies have no half steps to create friction, they sit comfortably over many different harmonies, which is part of why they show up so often in folk melodies, improvisation, and simple accompaniment lines.