Most improvisation is done in one of two basic frameworks:

1. The 12-bar blues.

2. The popular song.

There are other forms, particularly in contemporary improvisation, such as an agreement that improvisation will take place for 16 bars in the Dorian mode, 8 bars in the Lydian mode, then 8 bars in the Dorian Mode again. There is even a “free” form, where musicians just start playing and see what happens. But far and away the two main forms cover virtually all of improvised music today. Tomorrow we’ll take a look at the 12-bar blues form.