B, also known as Si, Ti, or, in some European countries, H,^[1] is the seventh note and the twelfth semitone of the fixed-Do solfège.^{[citation needed]} Its enharmonic equivalents are C♭ (C-flat) and A (A-double sharp).

When calculated in equal temperament with a reference of A above middle C as 440 Hz, the frequency of Middle B (B₄) is 493.883 Hz.^[2] See musical pitch for a discussion of historical variations in frequency.

The referent of the musical note B varies by location.^{[citation needed]} See Musical note § History of note names for a discussion on other differences in letter naming of the notes.

In the United States, Canada, Australia, the United Kingdom, the Republic of Ireland, and the Netherlands, as described above, B usually refers to the note a semitone below C, while B-flat refers to the note a whole tone below C.^{[citation needed]}

However, in Germany, Central and Eastern Europe, and Scandinavia, the label B is sometimes used for what, above, is called B-flat, and the note a semitone below C is called H. This makes possible certain spellings which are otherwise impossible, such as the BACH motif and the DSCH motif (the latter of which also uses the "S" name for what in Anglophone would be E-flat).^{[citation needed]}

• Piano key frequencies
• B major
• B minor
• Root (chord)