Rehearsal letter

A rehearsal letter is a boldface letter of the alphabet in an orchestral score, and its corresponding parts, that provides the conductor, who typically leads rehearsals, with a convenient spot to tell the orchestra to begin at places other than the start of movements or pieces. Rehearsal letters are most often used in scores of the Romantic era and onwards, beginning with Louis Spohr. Rehearsal letters are typically placed at structural points in the piece.

An example of rehearsal letters