B♭ (musical note)
B (B-flat) is the eleventh step of the Western chromatic scale (starting from C). It lies a diatonic semitone above A and a chromatic semitone below B, thus being enharmonic to A, even though in some musical tunings, B will have a different sounding pitch than A. B-flat is also enharmonic to C. When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of the B above middle C is approximately 466.164 Hz. See pitch (music) for a discussion of historical variations in frequency. While orchestras  tune to an A provided by the oboist, wind ensembles usually tune to a B-flat provided by a tuba, horn, or clarinet. In Germany, Russia, Poland and Scandinavia, this pitch is designated B, with 'H' used to designate the B-natural. Since the 1990s, B-flat is often denoted Bb or "Bess" instead of B in Swedish music textbooks. Natural B is called B by Swedish jazz and pop musicians, but still denoted H in classical music. See B (musical note) and Musical note#Note names and their history for explanations.