Scientific pitch notation is one of several methods that name the notes of the standard Western chromatic scale by combining a letter-name, accidentals, and a number identifying the pitch's octave. The definition of scientific pitch notation in this article is that proposed to the Acoustical Society of America in 1939,^[1] where C₀ is in the region of about 16 Hz.

Scientific pitch notation is a logarithmic frequency scale.

Scientific pitch notation is an example of a note-octave notation (see below).

The octave number increases by 1 upon an ascension from B to C, and "A₄" refers to the first A above middle C. In standard concert pitch, A_{4 is exactly 440 Hz, but the use of Scientific pitch notation to distinguish octaves does not depend on the pitch standard used.}

As an example, in ascending the white notes on a keyboard, C₄ immediately follows B₃.

Scientific pitch notation is often used to specify the range of an instrument. It provides an unambiguous means of identifying a note in terms of musical notation rather than frequency, while at the same time avoiding the transposition conventions that are used in writing the music for instruments such as the clarinet and guitar.

The conventional octave naming system — where for example C₀ is written as ′′C, or C,, or CCC in Helmholtz pitch notation, or referred to as subcontra C, and where C₄ is written as c′ or one-lined C — applies to the written notes that may or may not be transposed. For example, a d′ played on a B♭ trumpet is actually a C₄ in scientific pitch notation.

Although pitch notation is intended to describe audible sounds, it can also be used to specify the frequency of non-audible phenomena. For example, when the Chandra X-ray Observatory observed the waves of pressure fronts propagating away from a black hole, the one oscillation every 10 million years was described by NASA as corresponding to the B♭ fifty-seven octaves below middle C (or B♭₋₅₃).^[2]

Notation that appears to be scientific pitch notation may actually be based on an alternative octave numbering. While they are still note-octave systems, if they are called "scientific pitch notation", this is certainly an error. For example, MIDI software and hardware often uses C₅ or C₃ to represent middle C (note 60).^[3]

This creates a linear pitch space in which octaves have size 12, semitones (the distance between adjacent keys on the piano keyboard) have size 1, and A440 is assigned the number 69. Distance in this space corresponds to musical distance as measured in psychological experiments and understood by musicians. (An equal-tempered semitone is subdivided into 100 cents.) The system is flexible enough to include microtones not found on standard piano keyboards. For example, the pitch halfway between C (60) and C♯ (61) can be labeled 60.5.

The notation is sometimes used in the context of meantone temperament, and does not always assume equal temperament nor the standard concert A of 440 Hz; this is particularly the case in connection with earlier music.

The standard proposed to the Acoustical Society Of America^[1] explicitly states a logarithmic scale for frequency, which excludes meantone temperament, and the base frequency it uses gives A₄ a frequency of almost exactly 440 Hz (it comes out as approximately 439.96 Hz, which is a difference of 0.01 cents). However, when dealing with earlier music that did not use equal temperament, it is understandably easier to simply refer to notes by their closest modern equivalent, as opposed to specifying the difference using cents every time.

There is some possible confusion regarding the assignment of an octave to C♭ or B♯. The convention is that the letter name is first combined with the Arabic numeral to determine a specific pitch, which is then altered by applying accidentals. For example, the symbol C♭₄ means "the pitch one chromatic step below the pitch C₄" and not "the pitch-class C♭ in octave 4", so C♭₄ is the same pitch as B₃, not B₄. Similarly, at the other end of the fourth octave, B♯₄ is the same pitch as C₅, not C₄.

The matter may be clarified by viewing "♭" and "♯" as denoting lowering or raising by a variable amount. In equal temperament, that amount is exactly 2^1/12 ≈ 1.0594631, or 100 cents, whereas in quarter-comma meantone it is precisely 5^7/4/16 ≈ 1.0449067, or 76.049 cents, taking other values for other meantone tunings. Hence "C♭₄" is the same as "C₄♭", which in equal temperament is 100 cents below middle C, and equal to B₃. In quarter-comma meantone, C♭₄ is 76.049 cents below C₄ and 41.059 cents (ratio 128/125 = 1.024) sharper than B₃, which is 117.108 cents (ratio 8/5^5/4 = 5^7/4/15.625 ≈ 1.0699845) below C₄.

The table below gives notation for pitches based on standard concert pitch.

A musical initiative called scientific pitch is an absolute pitch standard that sets middle C (or C₄) to 256 Hz. It is not related to, or a part of scientific pitch notation described here, any more than 440 Hertz standard concert pitch. To avoid the confusion in names, scientific pitch is also called "Verdi tuning" and "philosophical pitch".

• Mathematics of musical scales
• Helmholtz pitch notation
• MIDI
• MIDI Tuning Standard
• Piano key frequencies
• Keyboard tablature
• Letter notation

• English Octave-Naming Convention – Music Theory Online