Key signatures, chords, scales, and phrases are said to be enharmonically equivalent if they contain the same pitches, but are notated differently.

Is there an analogous term to express that time signatures, meters, or rhythmic phrases are metrically equivalent when notated differently?

  • I like the suggestions in the answers, but I think there's actually a reason why, historically, there isn't a term for this but there is a term for the harmonic equivalent. Essentially, I think Western music theory focuses far more on harmony than on rhythm or melody. Additionally, there is a term for one common instance of this: hemiolas are temporary "rhythmic modulations" in which the rhythm of the piece temporarily matches that of a different key signature than the one it's actually written in. Apr 19, 2017 at 19:11
  • I didn't mean to suggest that "hemiola" works in the general case, and you're right that "isorhythm" has an established musical meaning that isn't quite what you're looking for, but as far as I can tell, "isometer" does not. Apr 20, 2017 at 13:32
  • Interesting; I hadn't found that. Apr 20, 2017 at 14:24

3 Answers 3


If you have durations with different rhythmic meaning in parallel (either due to polyrhythmic notation or because of using duplets or quadruplets), I'd lean towards calling them commensurate.


For some pieces of music from medieval days (or English descriptions of some Indian ragas), the term is isorhythmic. This may be commonly used in a more narrow sense than is being asked about. It applies to a rhythm pattern that is applied to a given tone sequence and repeated throughout a piece. If the lengths of tone sequence (called the color) and the rhythmic pattern (called the tala) differ, the entire pattern repeats after the LCM of their lengths. (I think the tala or rhythmic pattern is also called the hand.


I think that isorhythmic would be a good term and not introduce confusion.


I don't know of a term as universally used as "enharmonic" (I've never heard "enmetric," for instance), but with the use of algebraic group structures in music theory over the past few decades, the term "isomorphism" is becoming much more common.

Thus you may choose to say that the two key signatures, or two rhythmic profiles, etc. are "isomorphic."

  • "Isomorphism" can apply to essentially any "class" of thing, though--for instance "enharmonic" could be defined as harmonically isomorphic. So specifying "rhythmic isomorphism" would be good, I think. Perhaps "isorhythmic" or (to use an existing word) "isometric" would be even better. Apr 19, 2017 at 19:08
  • Isomorphism in mathematics just means something which can be "stretched" or "squeezed" to become the other thing. I'm not sure that's really the concept the OP wants to imply :-) . Apr 20, 2017 at 11:12

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