Rehearsal letter

Rehearsal letters are most often used in scores of the Romantic era and onwards, beginning with Louis Spohr.

In the course of rehearsing a symphony or piece, it is often necessary for the conductor to stop and go back to some point in the middle, in order to master the more difficult passages or sections, or to resolve a challenge that the ensemble is having.

For concert bands, rehearsal letters are placed over the piccolo's staff (or flutes'), and over the trumpets'.

For example, in some editions of Beethoven's Ninth Symphony, letter A of the Finale does not occur until bar 140, when the relatively late entry of the first violins with the "Ode to Joy" theme might not stand out enough to the other players to be a convenient point of reference, whereas the reminiscences of the previous movements' themes are more easily referenced by their tempo markings.

A rehearsal letter usually breaks a multimeasure rest in a part (except in cases where a given instrument does not play at all in a given movement of the work).

Because rehearsal letters are sometimes independent of edition and in some cases even version, they are also useful for telling applicants for positions in the orchestra what passages they need to play at the audition.

[7] Rehearsal letters are less useful in unaccompanied instrumental music such as the solo piano repertoire (although they may be used in duets), since the instrumentalist has no need to communicate to a fellow player where to resume playing.

[citation needed]But in the case of some composers, such as Gustav Mahler and Dmitri Shostakovich, twice through the alphabet might still not be enough.

Mahler actually wanted a pause of five minutes before the next movement, so the rehearsal numbers reset to 1, ending with 15.

[9] For jazz and pop compositions with several choruses, many jazz composers and arrangers use a format in which each successive verse/chorus part of the form is assigned successive letters of the alphabet combined with a measure number: for example, letter A for the first 8-bar phrase of the verse after the introduction, A9 for the next 8-bar phrase, A17, A25, then B, B9, B17, B25 for the chorus, etc., with the special rehearsal marking TAG for the tag ending.

From a page in the full score of Christoph Graupner 's Symphony in D major, Nagel 75. If the conductor wants to resume rehearsal from the second measure shown here, they could either say "measure 21" or "letter A".
From the bassoon part of Christoph Graupner 's Symphony in D major, Nagel 75. If the conductor says to resume playing from measure 21, the bassoonist has to count from measure 18, or count backwards from measure 23. But if the conductor says to resume from letter A, the bassoonist needs only find the letter A in his or her part.