in Islamic music, rhythmic modes—i.e., patterns of strong, intermediate, and weak beats, separated by pauses of various lengths. A well-developed system of such modes was described by medieval theorists. Although six or eight basic modes are included in most treatises, many more have actually been used.

The complete pattern, or period, repeated throughout the piece, is composed of smaller sections analogous to the feet of poetic metres. The various modes are said to be linked with the universe, and each has a character appropriate to music of a different mood.

Regularity of the rhythmic pattern is not obvious because the rhythmic accents do not necessarily coincide with melodic stresses. A voice or solo instrument carries the melody, while the rhythm is added by percussion or by slapping the knees. Pauses are often marked by gestures. The two lines (rhythm and melody) are united in the arrangement of large sections, but individual beats may clash. A rhythmic mode varies somewhat, and the tempo can be varied within traditional limits.

The īqāʿāt are in use in contemporary Arabic music. A system of rhythmic modes similar to īqāʿāt, called usul, is used in Turkish traditional classical music. Iranian music followed similar rhythmic principles in medieval times but now is much freer rhythmically.