Key signature key signatures showing sharps or flats on both octaves for notes which fall within the staff. An accidental is an exception to the key signature, applying only to the measure and octave in which it appears. Although a key signature may be written using any combination of sharp and flat symbols, the most common series of thirteen homogeneous key signatures—ranging from six flats to six sharps, with each successive flat or sharp placed on the note a perfect fifth below or above, respectively, the previous one—is assumed in much of this article. A piece scored using a single diatonic key
Scientific pitch notation frequencies, in other words, standard concert pitch and twelve-tone equal temperament). When a piano is tuned to just intonation, C refers to the same key on the keyboard, but a slightly different frequency. Mathematically, given the number formula_1 of semitones above middle C, the fundamental frequency in hertz is given by formula_2 (see twelfth root of two). Given the MIDI NoteOn number formula_3, the frequency of the note is normally formula_4 Hz, using standard tuning. Scientific pitch (q.v.) is an absolute pitch "standard", first proposed in 1713 by French physicist Joseph Sauveur. It was defined so that all Cs are