D♭ (D-flat) is a musical note lying a diatonic semitone above C and a chromatic semitone below D. It is thus enharmonic to C♯.
In the French solfège it is known as re bémol.
When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of middle D♭ (or D♭4) is approximately 277.183 Hz.
[1] See pitch (music) for a discussion of historical variations in frequency.
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