The second note ( supertonic) of the C major scale. In solfeggio, this note is called Re. The frequencies of the audible pitches of D are notated below. See also [Eng.] D; [Fr.] R' ; [Ger.] D; [It.] Re; [Sp.] Re.(1) the key of d (2) d numbers are used instead of opus numbers to catalogue works by Schubert