Atonally refers to music that lacks a tonal center, which means that it isn't based on any traditional music scales. However, there are a few different synonyms for atonal music, including dissonant, chaotic, erratic, or even experimental. These terms all describe music that moves away from traditional tonality and is marked by a lack of harmony, structure, or clear melody. Other similar words for atonal music might include abstract, avant-garde, unconventional, or unorthodox. Overall, these terms all suggest a break from traditional musical conventions and an experimentation with new sounds and styles.