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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.
1 hertz (Hz) 1 to 1.66 Hz: Approximate frequency of an adult human's resting heart beat: 1 Hz: 60 bpm, common tempo in music 2 Hz: 120 bpm, common tempo in music ~7.83 Hz: Fundamental frequency of the Schumann resonances: 10 1: 10 hertz 10 Hz: Cyclic rate of a typical automobile engine at idle (equivalent to 600 rpm) 12 Hz
Notes in it include a prime symbol below the note's letter. Names of subsequent lower octaves are preceded with "sub". Notes in each include an additional prime symbol below the note's letter. The octave starting at tenor C is called the "small" octave. Notes in it are written as lower case letters, so tenor C itself is written c in Helmholtz ...
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).
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.
Not only is 440 Hz the standard central pitch for MIDI, it is also widely used as the "concert A " standard pitch (A 4 e.g. USA, UK), and since that is represented in MIDI signals by the integer 69 (nine semitones above middle C (C 4, c′), which is 60 decimal or 0x3C hexadecimal), this gives a real number which expresses pitch in a manner ...
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]
Since this amounts to about 0.3% of the frequency which, near middle C (~264 Hz), is about one hertz, they could do it by using perfect fifths as a reference and adjusting the tempered note to produce beats at this rate. However, the frequency of the beats would have to be slightly adjusted, proportionately to the frequency of the note.