Flat
A flat lowers the affected written pitch by one semitone in ordinary 12-tone notation. As a note accidental it is written before the notehead; its duration follows the score's accidental convention.
- Accidentals
- Just before the note
- A curve or arc, A straight line
Do not confuse it with
A double flat lowers by two semitones, while a quarter-flat belongs to a specified microtonal system.
What the sources say
- Half Steps, Whole Steps, and Accidentals
A flat (♭) lowers a note by a half step.
- Music Fundamentals
Flat ... lowers pitch by half step
- SMuFL — Standard accidentals (12-EDO)
accidentalFlat — Flat