Middle C and Standard Pitch

 On Figure 3 you can see all registry ranges on piano. One range has the length of

one octave—so the distance between C3 and C4 is exactly one octave; samewith F2 — F3, D6 — D7, A4 — A5, etc. The distance between C1 and C3

would be 2 octaves, G4 and G7 3 octaves, etc. It’s important to remember here

that C is the starting note/frequency of each range, and that C4 note is called the

middle C. On guitar (if tuned to standard tuning), this note is found on the 5th

fret of the 3rd (G) string.

We use pitch to determine how high or how low something sounds. But there

was a problem back in history (before XIX century) when notes were not fixed

to certain pitches (pitch was not standardized), and musicians would just pick

certain frequencies according to their subjective hearing and assign notes to

them. For this, and many other reasons, it was obvious that pitch standardization

was needed. Throughout history there have been many attempts to standardize

the musical pitch. The most common modern music standard today sets the A

above middle C to vibrate at exactly 440 Hz. This A4 serves as the reference

note, with other notes being set relative to it. This is called the “Standard

pitch”, or “Concert pitch”. Most instruments today are tuned according to this

“default” tuning. On standardly tuned guitar for example, A above middle C is

found on the 5th fret of the 1st (thinnest high e) string.

Since A4 has the frequency of 440 Hz, what frequency would an octave lower—

A3 have?

The answer is: 220 Hz, and A5 would be 880 Hz.

This tuning standard is widely recognized and used, but there are also other

tuning choices used by different orchestras around the world, most of which

revolve around A4 being set to different frequencies, such as: 441 Hz, 442 Hz,

436 Hz, etc. There is another type of pitch standard, called Scientific pitch (or

Philosophical pitch), where the focus is put on the octaves of C rather than on A.

In Standard pitch, A4 is 440 Hz, and C4 (or middle C) is 261.625 Hz, but in

Scientific pitch C4 is adjusted so that it is equal to a whole number—256 Hz,

and A4 is 430.54 Hz. This pitch standard is sometimes favored in scientific

writings because 256 is a power of 2, which is very useful in the computer

binary system and serves different purposes.