List of works in irregular time signatures
Listed here are musical compositions or pieces in Western music that have unusual time signatures. "Unusual" is here defined to be any time signature other than simple time signatures with top numerals of 2, 3, or 4 and bottom numerals of 2, 4, or 8, and compound time signatures with top numerals of 6, 9, or 12 and bottom numerals 4, 8, or 16.
The conventions of musical notation typically allow for more than one written representation of a particular piece. The chosen time signature largely depends upon musical context, personal taste of the composer or transcriber, and the graphic layout on the written page. Frequently, published editions were written in a specific time signature to visually signify the tempo for slow movements in symphonies, sonatas, and concerti. The Piano Sonata No. 14 in C-sharp minor "Quasi una fantasia", Op. 27, No. 2, by Ludwig van Beethoven, popularly known as the Moonlight Sonata, includes two examples: in the relatively slow first movement the predominant rhythm is in triplet eighth notes (quavers), whereas in the second movement the basic tempo is faster but the music is notated in quarter notes (crotchets) and half notes (minims), giving a visual clue to the nature of the phrasing. The first movement could be written in 12
8 and still convey the same rhythm, phrasing, and tempo. Similarly, the second movement could be notated in 3
8 instead of 3
4 without changing the phrasing. More to the point of the present article, a perfectly consistent unusual metrical pattern may be notated in a more familiar time signature that does not correspond to it. For example, the Passacaglia from Britten's opera Peter Grimes consists of variations over a recurring bass line eleven beats in length, but is notated in ordinary 4
4 time, with each variation lasting 2 3⁄4 bars, and therefore commencing each time one crotchet earlier than the preceding one.
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