What was one such alternative to tonality or key centered music?

One alternative to tonality or key-centered music is atonal music. Atonal music is music that lacks a tonal center, or key. This means that the notes in an atonal piece do not gravitate towards a single tonal center, but instead exist independently of each other. Atonal music can be created using a variety of techniques, such as using dissonant chords, avoiding traditional melodic structures, and using aleatoric (chance-based) techniques. Atonal music is often associated with the early 20th-century classical music movement known as modernism. Some notable examples of atonal music include Arnold Schoenberg's "Pierrot Lunaire" (1912) and Alban Berg's "Wozzeck" (1925).