asymmetric metre
A time signature that cannot be divided into equal groups of two or three beats, such as 5/4 or 7/8
In Depth
Asymmetric or irregular metres combine groups of two and three in unequal patterns. 5/4 divides as 3+2 or 2+3; 7/8 divides as 2+2+3, 3+2+2, or 2+3+2. These metres are common in Balkan folk music, 20th-century art music, and progressive rock. Bartók, Stravinsky, and Messiaen all used asymmetric metres extensively. The uneven pulse creates a distinctive rhythmic energy that is impossible to achieve in regular metre, ranging from dancing lightness to driving intensity.
The theme from the TV show Mission: Impossible is in 5/4 time, making it one of the most recognisable pieces in an asymmetric metre.