Blue Bossa

Thirteen chords, one section, sixteen bars. It's the tune used to introduce a student to improvising — which is why almost nobody looks at it closely again.

Six tonal centres in thirteen chords. Three half-diminished. The modulation in the middle, which moves from one minor to another a half step away, is one of the most abrupt in the repertoire, and what gets played over it is usually the first mistake a student doesn't notice making.