1. The most common way to improvise in flamenco relates to the compás, which is playing the rhythmical bass, and you’re playing mostly chords. It’s supportive accompaniment, but it’s also driving the music forward. You are not only the drummer, but the entire band. Being the entire band means you have to play the chords, but there is room for improvisation. For example, let’s say you do some sort of I-IV-V thing to close a section. You can modify that—maybe you’ve rhythmically altered it with some countertimes or you put a few little cuts in there to make it interesting. The I-IV-V is still there in its essence, but you’ve changed it a little bit.
2. Another approach has to do with falsetas, these short, melodic musical phrases that are really complicated most of the time. To improvise one on the spot would be similar to a player like Sharon Isbin improvising a classical piece on the spot. Falsetas have to be practiced over and over again outside of performance. If you’re very lucky, there will be space in a song during the live performance where you can play it and hope that it works. It’s not very easy, but boy, when it happens right, it’s pretty magical. It’s one of my favorite things to do.
3. The third way is the most common among musicians, especially jazz musicians. People know the form of the song and everybody gets a turn. A guitar player would start with a single line and start working on a string and then start string-skipping and going around.—Ben Woods