Fugue sopra il Magnificat (BWV 733) – J. S. Bach (1685-1750)
From the Netherlands Bach Society web site:
Bach fools his listener with a quasi-fugue.
In view of the title Fuga sopra il Magnificat (this Sunday’s organ postlude in church), one would expect a more prominent function for the melody in this compact organ prelude. But the Gregorian Magnificat melody that Bach uses here is persistent. It evidently comes from a different musical era, which was still dominated by the old church modes.
We can even question whether or not this actually a fugue. What is certain, however, is that the ‘sopra’ in the title is to be taken literally. Here, it means ‘on top of’ or even ‘in between’, rather than its usual definition of ‘based on’. Bach cuts the melody of the Magnificat in two and then deliberately restricts himself to statements of the first half. Only at the last moment does he end the phrase in the pedal that suddenly springs into action. The fact is that the second half of the melody has a harmonic challenge: five times the same note, for which Bach has to find a creative solution in the upper parts.
Practical as ever, he juxtaposes a wealth of little motifs with the simple melody. For instance, throughout the piece we hear the recurring run from bar 2, just like the jumpy notes from bar 3, which can be inverted, extended, halved and doubled, etc. But little motifs do not make a fugue, or at least not a real one. Here, themes do not behave as they ought, and once the fugal box of tricks is opened it is more for the effect than to follow the rules of the art. And yet we fall for this ‘fugue’ with eyes wide open. Not bad for a young composer!