Notes & Pitch

The 12 Notes

Western music divides the octave into 12 equally spaced pitches, called the chromatic scale. Starting from C:

C - C#/Db - D - D#/Eb - E - F - F#/Gb - G - G#/Ab - A - A#/Bb - B

Each adjacent pair is separated by a half step (semitone), the smallest interval in standard Western music. Two half steps make a whole step (whole tone).

Enharmonic Equivalents

Most notes have two names. C# and Db are the same pitch spelled differently. Which name you use depends on the key and harmonic context. In the key of D major, you write F# (the third degree); in the key of Gb major, the same pitch is Gb (the root).

Octaves and Frequency

When you double a frequency, you get the same pitch class one octave higher. The note A4 vibrates at 440 Hz (the standard tuning reference). A5 is 880 Hz, A3 is 220 Hz. Every octave is a 2:1 frequency ratio.

Pitch Class

A pitch class groups together all octave-equivalent versions of a note. "C" as a pitch class includes C1, C2, C3, and every other C. There are exactly 12 pitch classes, and they repeat endlessly up and down the frequency spectrum.

MIDI and Scientific Pitch Notation

In scientific pitch notation, middle C is C4 (MIDI note 60). Each octave number increments at C, so B3 is immediately below C4. This system removes ambiguity when discussing specific pitches across instruments.

On the Guitar

In standard tuning, the open strings span almost four octaves. In fourths tuning (E-A-D-G-C-F), the open strings cover a slightly wider range and are spaced with perfect geometric regularity, which means the same interval shape works identically on every pair of adjacent strings.