Besides the 12-bar Blues, jazz has another equally important "chord skeleton" — 32-bar AABA. This progression became famous through George Gershwin's 1930 song "I Got Rhythm", so musicians simply call it Rhythm Changes. This page only teaches chord symbols and Roman numerals (just like a textbook) — no melody or lyrics involved.
Ready
One cell per bar; the lit cell follows the playback. The bridge (warm color) is four dominant 7th chords descending in sequence, changing every two bars — listen for that feeling of being pushed steadily forward.
Short, slow harmonic rhythm (often one chord per bar), just 3 chords, and the whole tune repeats the same 12 bars. Good for a beginner's first improvisation.
More than twice as long as the Blues, the form splits into four A-A-B-A sections, the bridge's harmonic rhythm speeds up (a new chord every two bars), and there are more chord types — the next milestone for advancing improvisers.
How is it applied? Recognize this skeleton and you've learned the harmonic basis of a whole batch of jazz standards at once — they're all built on the same A-A-B-A progression, just with different tempos, keys, and embellishments. The following titles are for reference only (no melody or lyrics involved):
Using it to improvise: for the A section, use the major/Dorian scales you learned in the Scale Lab; every chord in the bridge is a dominant 7th, so try laying Mixolydian (major with a flat 7) over each of the four chords and hear how the descending cycle keeps pushing the music forward.