unpredictable
Nachtmusik
absolute music
accidental
adaptation
adventitious
adventurous
air varie
aleatoric
aleatory music
amorphous
arrangement
blobby
blurred
blurry
broad
casual
causeless
chamber music
chamber orchestra
chance
chancy
chaotic
circumstantial
composition
conditional
confused
contingent
descant
destinal
dicey
disordered
electronic music
etude
exercise
fatal
fatidic
fluky
foggy
fortuitous
full of risk
fuzzy
general
harmonization
hazardous
hazy
hit-or-miss
iffy
ill-defined
imprecise
inaccurate