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This is a list of the fundamental frequencies in hertz (cycles per second) of the keys of a modern 88-key standard or 108-key extended piano in twelve-tone equal temperament, with the 49th key, the fifth A (called A 4), tuned to 440 Hz (referred to as A440). [1] [2] Every octave is made of twelve steps called semitones.
"Frequency data shall be defined in [units] which are fractions of a semitone. The frequency range starts at MIDI note 0, C = 8.1758 Hz, and extends above MIDI note 127, G = 12543.854 Hz. The first byte of the frequency data word specifies the highest equal-tempered semitone not exceeding the frequency.
Likewise, if a string tuned to 220 Hz (with a harmonic at 440 Hz) is played together with a string tuned at 442 Hz, the same 2 Hz beat is heard. [4] Because pianos typically have multiple strings for each piano key, these strings must be tuned to the same frequency to eliminate beats.
Notes in each include an additional prime symbol below the note's letter. The octave starting at middle C is called the "small" octave. Notes in it are written as lower case letters, so middle C itself is written c in Helmholtz notation. The next higher octave is called "one-lined". Notes in it include a prime symbol above the note's letter.
For instance, 660 Hz / 440 Hz (a ratio of 3:2) constitutes a fifth, and 880 Hz / 440 Hz (2:1) an octave. Such intervals (termed "just") have a stability, or purity to their sound, when played simultaneously (assuming they are played using timbres with harmonic partials) because pure intervals do not waver or beat regularly.
An 88-key piano, with the octaves numbered and middle C (cyan) and A 4 (yellow) highlighted. A440 is widely used as concert pitch in the United Kingdom [8] and the United States. [9] In continental Europe the frequency of A 4 commonly varies between 440 Hz and 444 Hz. [8]
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The purpose of this adjustment is to move the 12 notes within a smaller range of frequency, namely within the interval between the base note D and the D above it (a note with twice its frequency). This interval is typically called the basic octave (on a piano keyboard, an octave has only 12 keys).