quarterflat

Quarter-flat is a term used in microtonal music to describe a pitch that is lowered by a quarter of a semitone relative to its standard equal-tempered pitch. In practical terms, a quarter-flat note is about 50 cents below the natural pitch, placing it roughly halfway between the unaltered note and its ordinary flat in 12-tone tuning. This type of alteration is most commonly encountered in tuning systems that divide the octave into more than the usual 12 equal steps, such as 24-tone equal temperament (24-TET), where each step is a 50-cent interval.

Notation for quarter-flat pitches varies by system and publisher. A dedicated quarter-tone accidental is often used, appearing as a flat symbol with a diagonal slash or other distinct markings intended to indicate a 50-cent lowering. Some editions employ composite accidentals or alternate spellings to represent quarter-flat notes, and performers rely on microtonal tunings or electronically generated pitches to render them accurately.

Quarter-flat intervals broaden the chromatic palette available to composers and performers, enabling closer approximations to just intonation or other microtonal temperaments. They are particularly associated with experimental, contemporary classical music and with traditional practices that explore flexible pitch systems. In practice, realizing quarter-flat pitches requires instruments or playback systems capable of microtonal tuning, such as dedicated keyboards, electronic synthesis, fretless strings, or carefully adjusted acoustic instruments.