Semitone

Minor second on C

File:Minor second on C.mid

Cadence minor second

File:Cadence minor second V65-I.mid

Bach minor second smaller

File:Bach minor second smaller BWV 846.mid Semitone is the smallest interval used in classical Western music, dividing the octave into twelve equal parts. It is the building block of the chromatic scale, and in the equal temperament tuning system, all semitones have the same size. However, in other tuning systems, such as just intonation or meantone temperament, the size of a semitone can vary. Semitones can be further classified into two types: the diatonic semitone, or minor second, which occurs between two adjacent notes with different names (e.g., C to D♭); and the chromatic semitone, or augmented unison, which occurs between two notes with the same name but different accidentals (e.g., C to C♯).

Types of Semitones

There are two main types of semitones in Western music theory:

• Diatonic Semitone: This type of semitone is found between two notes that are a step apart in the diatonic scale, with one being a natural note and the other being either a sharp or flat. For example, the interval from E to F in the C major scale is a diatonic semitone, as there is no black key between them on the piano.

• Chromatic Semitone: The chromatic semitone occurs between two notes that have the same letter name but differ in accidental, such as G to G♯. This type of semitone is used to alter the pitch of a note within the same diatonic scale degree, adding chromaticism to the music.

Usage in Music

Semitones are fundamental to the structure of Western music, allowing for the creation of a wide range of harmonies and melodies. They are essential in the development of musical tension and resolution, which is a core aspect of Western music's expressiveness. The semitone's dissonant quality when played in succession or harmony makes it a powerful tool for composers and musicians.

In harmony, semitones are often found leading into the resolution of a chord progression, with the leading tone resolving up by a semitone to the tonic in tonal music. This creates a sense of closure and rest. In melody, semitones are used to create expressive nuances and to navigate through different tonalities and modes.

Tuning Systems and the Semitone

The size and nature of a semitone can vary depending on the tuning system in use. In the equal temperament system, which is the most common system used in Western music today, the octave is divided into twelve equal semitones. This allows for the easy modulation between keys but at the cost of perfect consonance in intervals like the major third and perfect fifth.

In other tuning systems, such as just intonation, semitones can have slightly different sizes. These systems aim to align intervals more closely with the natural harmonic series, resulting in purer consonances but making modulation more complex.

See Also

• Chromatic scale
• Diatonic scale
• Equal temperament
• Just intonation
• Meantone temperament
• Musical interval
• Octave
• Tuning system