2. Accidental music:

It refers to the composer intentionally giving up subjective control of certain parameters (pitch, rhythm, structure) in the music when creating music, and using some It can be determined objectively (such as tossing a coin, doing gossip, flipping cards, etc.), or it can be left to the performer to improvise during the performance. This music is characterized by a certain degree of uncertainty in the music.

Mei and Cage "4 Minutes and 33 Seconds"