Johann Sebastian Bach loved to put unexpected themes and obscure references in his music. Most famous of these is the fact that he often put his name in his music (in the main theme or elswhere.) Although in English there is no such note as 'H', in German, H is B (And "B" is the German for the English B flat), so Bach often used the notes 'Bb A C B' in his music, perhaps as a sort of private humour.
In the last page of Bach's 'Art of Fugue, Bach brought in his name as a countersubject. At that point, he died.

See also Godel, Escher, Bach by Douglas Hofstadter.