INTRODUCTION

• In music of the West, the octave is divided into 12 equal parts called half steps, or semitones.

• In non-Western music, the octave may be divided into 24 units (quartertones).

• In some more modern Western music, it may be divided into even smaller units (microtones), as in the 43-unit music by American composer Harry Partch.

• The white keys on a piano are separated by black keys except for E to F and B to C.

• All adjacent numbered keys are called half steps (HS). Half steps are paired white to black keys, or black to white keys, except for the two adjacent pairs of white keys (E to F and B to C).

• Two adjacent half steps comprise a whole step. On the keyboard, skip one key between two notes to create a whole step.

• Diatonic whole steps consist of two half steps with adjacent letter names.

ENHARMONIC SPELLINGS

• All notes have at least two letter names called enharmonic spellings. Enharmonic pitches sound the same but have different names.

• Enharmonics may be compared to homonyms in English, words that sound the same, but have different meaning and spelling.

  • F sharp and G flat are enharmonic names for the same black key.

  • B sharp and C are enharmonic names for the same white key.

DIATONIC AND CHROMATIC HALF STEPS

• Notes forming a half step may be written in two ways: both notes may be written using the same letter name or the notes may be written with two consecutive letter names.

  • For example, the half step F to F# may also be written F to Gb.

• If the letter names are different consecutive letters, the half step is called a diatonic half step (di = two). If the letter names are the same, this is called a chromatic half step (chroma = color).

CHROMATIC SCALES

• A scale is a pattern of notes. When a scale consists only of notes that are half steps apart, this is called a chromatic scale.

• Properties of a chromatic scale:

  • All pitches are a half step apart.

  • When notating an ascending chromatic scale, sharps are usually used to identify black keys. When descending, flats are usually used.

  • There are 12 different pitches in a chromatic scale; the thirteenth pitch is the octave note.

  • Although this is called a chromatic scale, both chromatic half steps (C–C#) and diatonic half steps (C#–D)are used.

    • Note that diatonic spellings usually are used for the two pairs of white key half steps, E–F and B–C.