Which musical element can be found in both active and passive beats?

The concept of simple pulses is integral to both active and passive beats within music. Simple pulses serve as the foundational rhythm upon which other elements of music are built. They create an underlying steady beat that can be felt throughout a piece of music, regardless of whether the accompaniment is actively driving the rhythm or passively maintaining a consistent tempo.

In the context of active beats, the simple pulse tends to be more pronounced, often highlighted by instruments or voices emphasizing rhythmic patterns. On the other hand, in passive beats, while the rhythmic activity may be less prominent, the simple pulse continues to provide a steady framework, allowing for a sense of timing and structure.

The other musical elements listed do not have the same universal application across both types of beats. Rhythmic variety typically refers to variations and complexities introduced in rhythm, which might not always align with the steady nature of simple pulses. Melodic improvisation, while creative and vital in many musical styles, is more about the exploration of melody rather than foundational rhythm. Tempo indication reflects the speed at which music is played but does not embody the essence of both active and passive rhythmic behaviors like simple pulses do.