D is a musical note a whole tone above C, and is known as Re within the fixed-Do solfege system. An enharmonic note is C
When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of middle D (D4) is approximately 293.665 Hz. See pitch for a discussion of historical variations in frequency.
|Scientific designation||Helmholtz designation||Octave name||Frequency (Hz)|
|D−1||D͵͵͵ or ͵͵͵D or DDDD||Subsubcontra||9.177|
|D0||D͵͵ or ͵͵D or DDD||Subcontra||18.354|
|D1||D͵ or ͵D or DD||Contra||36.708|
We use the note D as the standard note, Dorian mode as the standard mode, and the conjugates are: D self, A-G, E-C, B-F, F#-Bb, C#-Eb, G#-Ab (enharmonic equivalent), ... (the (white or black) keys on the piano are symmetry)