How does microtonal music use intervals smaller or larger than the equal-tempered semitone?

Microtonal music utilizes intervals that differ from the standard 100-cent semitone found in equal temperament. While the term implies a departure from Western norms, many global musical traditions have long employed intervals both larger and smaller than the conventional half step.1

Methods of using these intervals include:

• Non-Western Traditions: Many cultures utilize unique tuning systems, such as the South Asian scale of 22 unequal intervals or the Indonesian slendro scale, which divides the octave into five roughly equal intervals of 240 cents each. Middle Eastern music frequently incorporates intervals of 150 cents (three-quarter tones) and 250 cents (five-quarter tones).1
• Western Experimentalism: Composers often derive microtonal intervals by subdividing the standard 100-cent semitone. Common examples include quarter tones (50 cents), 6th tones (33.3 cents), 12th tones (16.7 cents), and 16th tones (12.5 cents). In a 16th-tone system, the octave is divided into 96 equal parts.1
• Theoretical Structures: Some systems incorporate specific ancient intervals, such as the comma (24 cents) and limma (90 cents), to build complex harmonic or melodic structures.1