Beat Prototypes


URrhythm — represent Johnson-Laird beat prototypes for a passage


The URrhythm representation encodes beat "prototypes" (Ur-rhythms) evident in a musical passage. The representation is based on Johnson-Laird’s theory of rhythmic prototypes (see REFERENCES below).

The URrhythm representation characterizes each beat in a passage as belonging to one of three "beat types": Note (N), Syncopation (S), or Other (O). Only principle beats are characterized in this way. Hence, in 3/4 or 9/8 meters, three beats are characterized for each complete measure. Similarly, in 4/2 and 12/16, four beats are characterized for each complete measure. Johnson-Laird’s rhythmic-prototype theory can be applied only to musical passages conforming to regular meters (simple and compound, duple, triple and quadruple).

A "Note" (signified in the output by the letter `N') is defined as a beat that coincides with a note onset.

A metric "Syncopation" (signified by the letter `S') is defined as arising when no note-onset happens on a beat whose metric position is more important than that of the most recent note onset. By way of example, imagine a measure in 4/4 meter containing a quarter-note, followed by a half-note, followed by a quarter-note. The third beat position does not coincide with a note onset. The most recent note onset prior to the third beat occurs on beat two. Since beat three is a more important metric position than beat two, beat three is deemed to be syncopated.

Metrically syncopated beats can happen only after the first note onset; subsequent syncopated moments require another note onset (i.e. two syncopated moments can’t occur in a row without some note onset intervening).

An "Other" (signified by the letter `O') is any beat that is not a Note (N) or a syncopation (S).

Barlines are represented using the "common system" for barlines — see barlines.


It is recommended that files containing predominantly URrhythm data should be given names with the distinguishing `.urr' extension.


The following table summarizes the URrhythm mappings of signifiers and signifieds.

N "note" beat prototype O "other" beat prototype S "syncopation" beat prototype . null token = barline; == double barline 0-9 measure numbers —– ——————————–

Summary of URrhythm Signifiers


A sample document is given below:


**URrhythm *M4/4 *tb8 N . N . S . =1 N . O . S . O . =2 S . S . O . N . *- ————–


The following Humdrum command produces URrhythm data as output:

urrhythm characterize the rhythmic prototypes in a passage – ——————————————- —————————————————


The following tandem interpretations can be used in conjunction with URrhythm:

meter signatures *M6/8 tempo *MM96.3 timebase *tb32 —————— ———–

Tandem interpretations for URrhythm


barlines, **metpos, metpos, urrhythm, **synco, synco, **timebase



Philip Johnson-Laird, "Rhythm and meter: A theory at the computational level," Psychomusicology, Vol. 10 (1991) pp. 88-106.

Jasba Simpson & David Huron, "The perception of rhythmic similarity: A test of a modified version of Johnson-Laird’s theory," Canadian Acoustics, Vol. 21, No. 3 (1993) pp. 89-90.