Flat
A flat lowers a note by a half step (a semitone). B flat is the note a half step below B.
How to read it
The flat sign, which looks like a lowercase b, is written just before a note or in the key signature at the start of the staff. A double flat lowers the note by two half steps, a whole step. A Natural cancels a flat.
In the key signature or beside a note
Sharps and flats grouped at the start of each staff are the key signature: they apply to every note on those lines and spaces, in every octave, until the key changes. One written just before a note is an accidental. It applies to that note and to later notes on the same line or space until the next barline.
Where the shape comes from
The flat began as a letter b. In medieval Latin, B flat was B rotundum or B molle and B natural was B durum, and Stainer and Barrett’s dictionary (1898) says the flat’s shape comes from that old b. In German, B flat is called “B” and B natural “H”.
Look-alikes
The flat looks like a b, but a narrower, pointed one: its bowl tapers to a point at the foot of the stem.
More music symbols
Sources
- Music Theory for the 21st-Century Classroom: Accidentals, Robert Hutchinson, section 1.4, University of Puget Sound, Section 1.4
- Music Notation and Terminology, Karl W. Gehrkens, 1914, A. S. Barnes Company (Project Gutenberg), Chapter II, §19, footnote 6
- Primer of Facts about Music, M. G. Evans, 1909, Theodore Presser Co. (Internet Archive, University of Toronto), Q. 24
- Stainer and Barrett's Dictionary of Musical Terms, John Stainer and W. A. Barrett, new and revised edition, 1898, Novello (Internet Archive, Cornell University Library), Flat; B rotundum; B durum
Last reviewed September 26, 2026 by Rory Hansen. How we research