B♭ (musical note)

B♭ (B-flat; also called si bémol) 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#History of note names for explanations.

Designation by octave

Scientific designation	Helmholtz designation	Octave name	Frequency (Hz)
B♭₋₁	B♭͵͵͵ or ͵͵͵B♭ or BBBB♭	Subsubcontra	14.568
B♭₀	B♭͵͵ or ͵͵B♭ or BBB♭	Subcontra	29.135
B♭₁	B♭͵ or ͵B♭ or BB♭	Contra	58.270
B♭₂	B♭	Great	116.541
B♭₃	b♭	Small	233.082
B♭₄	b♭′	One-lined	466.164
B♭₅	b♭′′	Two-lined	932.328
B♭₆	b♭′′′	Three-lined	1864.655
B♭₇	b♭′′′′	Four-lined	3729.310
B♭₈	b♭′′′′′	Five-lined	7458.620
B♭₉	b♭′′′′′′	Six-lined	14917.240
B♭₁₀	b♭′′′′′′′	Seven-lined	29834.481

Scales

Common scales beginning on B♭

B-flat major: B♭ C D E♭ F G A B♭
B-flat natural minor: B♭ C D♭ E♭ F G♭ A♭ B♭
B-flat harmonic minor: B♭ C D♭ E♭ F G♭ A B♭
B-flat melodic minor ascending: B♭ C D♭ E♭ F G A B♭
B-flat melodic minor descending: B♭ A♭ G♭ F E♭ D♭ C B♭

Diatonic scales

B♭ Ionian: B♭ C D E♭ F G A B♭
B♭ Dorian: B♭ C D♭ E♭ F G A♭ B♭
B♭ Phrygian: B♭ C♭ D♭ E♭ F G♭ A♭ B♭
B♭ Lydian: B♭ C D E F G A B♭
B♭ Mixolydian: B♭ C D E♭ F G A♭ B♭
B♭ Aeolian: B♭ C D♭ E♭ F G♭ A♭ B♭
B♭ Locrian: B♭ C♭ D♭ E♭ F♭ G♭ A♭ B♭

Jazz melodic minor

B♭ ascending melodic minor: B♭ C D♭ E♭ F G A B♭
B♭ Dorian ♭2: B♭ C♭ D♭ E♭ F G A♭ B♭
B♭ Lydian augmented: B♭ C D E F♯ G A B♭
B♭ Lydian dominant: B♭ C D E F G A♭ B♭
B♭ Mixolydian ♭6: B♭ C D E♭ F G♭ A♭ B♭
B♭ Locrian ♮2: B♭ C D♭ E♭ F♭ G♭ A♭ B♭
B♭ altered: B♭ C♭ D♭ E F♭ G♭ A♭ B♭

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