atonal

US /ˌeɪˈtoʊ.nəl/
UK /ˌeɪˈtoʊ.nəl/
"atonal" picture
1.

not written in any key or mode; lacking tonality.

:
Schoenberg's early works were revolutionary for their atonal compositions.
The modern piece of music was entirely atonal, challenging the audience's traditional expectations.