We take another trip to Leipzig for this homework!
All material comes from the second fugue from the first book of the Well-Tempered Clavier (BWV 847). This is a wonderful triple fugue that exemplifies the brilliance of Bachs' writing.
My goal is to recreate the exposition for this fugue, almost verbatim, while demonstrating the effect of a streaming illusion. The illusion is particularly compelling since the voices are largely independent.
I encode the subject, first counter subject, subject variation, counter subject inversion and second counter subject as their MIDI key numbers in fugue.ck. The various parts are analyzed and pointed out below.
Where possible I have minimized the need for transcribing new parts by manipulating (transposing) existing parts. This was unfortunately not possible for the inversion of the counter subject since it is not a literal inversion.
The composition begins with the subject and counter subject being played 40 times under tempo. After 10 seconds of this, we speed up to the regular tempo and the voices become distinct. The subject and counter subject are then restated at this tempo.
After this short introduction I introduce the inversion of the counter subject. The IOI is modulated such that the illusion is taken to an extreme and every group of notes becomes a pitch momentarily. Once this happens, I modulate the IOI back to tempo (or below it). We introduce the final entry of the subject in the bass voice, and end the composition by restating the subject and counter subject.
A class named Instrument is introduced which abstracts FMFS into a class that exposes an interface similar to other instrument interfaces in ChucK. We construct two FM instruments with irrational modulation ratios and one with a rational ratio.
Fugue