What do these square brackets, triangles, and the numbers next to them mean, in Le Marteau sans maître by Pierre Boulez.
2Finding the source may be critical. This could be some custom rhythm notation for a non-standard music instrument. The digit seems to represent number of notes in a measure, ⎵ is a quarter note, triangle is a dotted quarter note, | is an eighth note.– user1079505Oct 10, 2022 at 19:21
6@user1079505 a nonstandard instrument known as a "conductor."– phoogOct 10, 2022 at 20:05
4@user1079505 This kind of notation is standard for orchestra musicians and conductors to mark their parts/scores where the beat pattern would be otherwise unclear. It's very unusual to see it printed in a score: normally it's the conductor's decision how they want to conduct.– PiedPiperOct 10, 2022 at 20:32
@PiedPiper ah thanks, this clarifies! Indeed I don't recall seeing such marks in scores, but this seems a modern composition with frequent and irregular time signature changes, likely challenging to conduct!– user1079505Oct 10, 2022 at 20:37
2@user1079505 I've found the source, it's Le Marteau sans maître by Boulez. Anyway thanks for the help from all of you and hope this clarifies.– Jiewei XiongOct 11, 2022 at 13:06
Lazy's answer is almost correct. The 2 and 3 at the beginning of each measure indicates the pattern to be conducted. The geometric figure indicates the duration of each beat. The square U indicates a quarter note (two eighths); the triangle indicates a dotted quarter (three eighths), and the single vertical stroke indicates one eighth.
See also my recent answer to the closely related question Is there a standard way to conduct 5/4 and 7/4, amongst other irregular time signatures?
These are conducting marks. A lines means one beat, a |_| shape means two beats, a triangle means three beats, a |_|_|_| four beats. In this case this does not refer to the actual beats of the measure, but to an 1/8 note subbeam structure.
So most likely the conductor is supposed to conduct one two beat gesture and one three beat gesture for the first measure, three two beat gestures for the second one and so on. The number indicate how many such subbeat divisions are within the current measure.
1Is it a standard notation for conducting? Oct 10, 2022 at 20:00