Avant-garde/Experimental/Drone/Non-Music... The weirdest you've got

https://www.youtube.com/watch?v=ipUoRpVK32s&t=177s

this is not a bad explanation either

I get Nyman's definition.

I've always taken-away from "experimental" the meaning that "some of this performance will consist of very deliberate fucking around with unpredictable results"-- not the same as improvisation, but rather the opposite-- the composer/performer will engage in a process that allows for an unpredictable outcome, a controlled loss-of-control.

As for "avant-garde" I just relate it to the traditional pre-20th c. version of what I think it means. The composition will deliberately subvert the notion of composition in order to make an oblique statement and/or commentary on the nature of composition itself (and society etc.)

Improvised - musicians have meticulously trained themselves to be able to make shit up on the spot and make it great and do so in controlled environments with well-tuned instruments.

Experimental - bored of improvising, musicians will subvert their training by performing improvised music while running through an area deemed unsafe, due to radioactivity

Avant-Garde - I carry the corpse of the now-deceased musician to the concert hall and dump it on the stage while whistling "Figaro" and take a bow to wild applause

My understanding mirrors fgti's. 'Experimental' loosely implies the scientific method, whereas 'avant-garde' is a bellicose, combative stance, whether aesthetic or political (oftentimes both).