I have occasionally delved into the impossible task of classification. When you try to do something that can't be done, you will discover that you cannot do it. Still, the resulting errors are at least entertaining to myself.
Irène Schweizer is a Swiss pianist whom I discovered just tonight, after downloading her duet album with drummer Han Bennink. I haven't had time to digest the whole album yet, but the second cut is simply magnificent. Schweizer is described as a free jazz musician, but 'Verzweigelt' (desperation) seems to me to be a showpiece of avant garde.
I like to keep classifications as neat as possible, and here is how I see the two sub-genres of jazz. Free jazz is improvising that is unencumbered (by melody, time signatures, etc.) either externally by an prearranged form or internally as the music proceeds. Avant garde is jazz that is fundamentally abstract, taking music apart and rearranging it according to the forms rather than the narrative. The two types of music are not exclusive; however, when some kind of story line emerges, it is more proper to call it avant garde.
It seems to me that 'Verzweigelt' surely finds a story. While challenging, I think it is not that hard to follow and it is warm and compelling. The above is not so good a sample, but it's mighty fun to watch. I am also playing 'Eine andere Partie Tischtennis'.