Rhythm.

Rhythm is one of the most important components of music. Music can have no melody or tones, but it can never be separated from rhythm. The earliest human music had only rhythm or was rhythm-based. Among the existing folk music, there is also music using only percussion instruments. This shows that apart from the fixed pitch notes, the rhythm itself has great expressive power and has independent "rhythmic beauty". In this case, rhythm is the only "lifeline" of music.