- C♯ (musical note)
C♯ (C-sharp) is a musical note lying a chromatic semitone above C and a diatonic semitone below D. C sharp is thus enharmonic to D♭ (D♭). It is the second semitone in the French solfege and is known there as Do Dièse.
When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of C♯4 (the C♯ above middle C) is about 277.18 Hz. See pitch (music) for a discussion of historical variations in frequency.
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