Math in the Musical Offering
g(t) = f(t-1) + H and Canon 5
In Canon 5 the second voice follows one measure behind, just asin Canon 2, but it is shifted up in pitch by a perfect fifth. In Bach's encryption of this canon, theshift is indicated by the two clefs in the lower staff.
Graphic © 1996, Timothy A. Smith, used by permission.
The first voice is readusing the bass clef, the second with the same notes but using the altoclef (centered on middle C). A modified ``royal theme'' plays in the top staff,in harmony with the two lower voices.
The mathematical analogue of a canon where Voice 2 starts one measureafter Voice 1 and is shifted up a perfect fifth is a pair of functions f(t) and g(t)with g(t) = f(t-1) +H,
if the tunit is a measure, and where H is the distance along the pitch axis representing ``up one fifth''.
This canon has another unusual feature which is not duplicated in thegraphs:It does not recycle periodically, but each successive run-through is modulatedupward in pitch by a whole step.
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