Which term describes a beat that is divided into three, such as in 6/8 time signature?

The term that accurately describes a beat that is divided into three, as seen in a 6/8 time signature, is indeed the one referring to compound time groupings. In compound time signatures, each beat is subdivided into three equal parts, which creates a flowing, triplet feel. In the case of 6/8, there are six quaver notes in a measure, which are grouped into two beats, with each beat divided into three quavers. This structure gives 6/8 its characteristic rhythmic pattern, often associated with lively and dance-like music.

In contrast, simple time would involve beats that are divided into two, like 4/4 or 3/4. Mixed meter refers to a combination of different time signatures used within a piece of music but does not specifically address the division of beats into three. Quadruple time focuses on meter that has four beats per measure, such as in 4/4 or 4/2, and does not describe the subdivision relevant to 6/8.

Thus, recognizing compound time groupings is crucial for understanding how rhythms are structured in different musical contexts, especially those that feature a triplet feel.