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The chromatic scale divides the octave into 12 equal semitones, one for each adjacent key on the keyboard

Fact L1Foundations A · Music theory & musicianship

The interval between any two adjacent notes on the keyboard (or adjacent frets on a guitar) is called a semitone. An octave contains exactly 12 semitones. The chromatic scale lists all 12 in succession. Two semitones equal a whole tone. The chromatic scale is not used as a standalone musical scale for melody but serves as the master pool of pitches from which modal and diatonic scales are selected. Understanding semitones is essential for: transposing scales, understanding key signatures, working with MIDI note numbers, and applying the major/minor scale formulas.

Examples

C to C# = 1 semitone. C to D = 2 semitones (1 tone). E to F = 1 semitone (adjacent, no black key between them).

Assessment

Count the semitones from C to G. From A to C. Explain why there is no black key between E and F or between B and C.

Prerequisites — understand these first

Pitch is the singable 'how high or low' quality of a sound, distinct from noise you can only call high or low

Don't confuse with

The octave is divided into 12 equal semitones, giving 12 distinct pitch classes

Sources

“called asemitone(see Figure 3.5).”

corpus · michael-hewitt-music-theory-for-computer-musicians · chunk 9

Taught in modules

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