If you shouted "evolutio" in a theater full of musicians, they wouldn't know whether to run from the fire or stand on their heads...not even most composers! But Johann Sebastian would have known! I first encountered the term when studying his Fourteen Canons on the Goldberg Ground--one of your listening assignments for the second week. Maybe you remember seeing that word with Canon No. 10. Recall that No. 10 was not really a canon, but two lines that could be played rightside-up or upside-down. Of course, when you turn the music upside-down, what had been the high voice becomes the low and vice versa (contrapuntal inversion). Not only so, but what had been a descending interval now ascends and vice versa (melodic inversion). It is this contrapuntally and melodically inverted creature that Bach called the Evolutio. To my knowledge, it is the only place he uses the term in the literature extant.
Two-Part Invention No. 1 in C Major: If you haven't ejected the Art of Fugue disk, do that now and reinsert the Inventionen & Sinfonien. Study the example carefully as, in the homework, you will be asked to identify the measures in which these fragments occur.
Well, that about wraps up our look at textural procedures that can be used to "invent" longer works out of short ideas. While Bach-style inventions are normally studied as a FORM--with a well-defined order of motives, countermotives, expositions, developments and the like--my purpose here has been to see, in them, a PROCESS, essentially developmental, which we will revisit often in the works of composers as diverse as Mozart and Stravinsky. All that remains is to do Homework Assignment No. 4.
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©1996 Timothy A. Smith
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