BB♭, or B-flat, is a musical note that is one semitone lower than B natural. It is commonly used in various musical contexts, including orchestras, bands, and solo performances. The note is represented on the piano as the black key immediately to the left of the B key. In Western music, BB♭ is often associated with the key of F major and B♭ major, which are frequently used in compositions. Instruments like the trumpet and saxophone are commonly tuned to B-flat, meaning they sound a whole step lower than written.