Currently listening to "The Master", in arrangements for different instruments than the original. The arrangements are meant as an educational vid on how a fugue works, this is supported by showing the different voices in a various colour block graph (as creaded by midi).
In the first piece, The four color groups indicate the four instruments (oboe, English horn, bass clarinet, bassoon), and for each color group, the dark, vivid color shows when an instrument has the theme (the first tones you hear before another voice comes in are the "theme"). The theme appear for upright (normal) and inverted (up and down motion are reversed, but all the intervals stay the same).
The piece starts simple and gets more complicated as it proceeds:
0:07 -
0:53 is the "exposition," in which the theme gets presented in all voices (they play it sequentially, each voice chiming in after the oterh has finished it);
1:05 -
1:29 is the first "stretto" section, in which two voices at a time have the theme overlapping;
1:37 -
2:23 is the "inverted exposition," in which each voice presents the theme inverted;
2:32 -
2:56 is the "inverted stretto," in which two voices at a time play the inverted theme;
3:01 -
3:31 is the "combined stretto"; one voice plays the inverted theme and one voice plays it as when started;
3:37 -
3:48 is a "doubled combined stretto," with each version of the theme played by two voices.
The few parts where the theme is not being played are called "episodes," and give you a breather while you wait for the theme to return (and the composer time to synchronize the voices for the next variation on the theme).
[ame="http://www.youtube.com/watch?v=k-w_prKGo5Y"]Bach, Fugue 22, Well-Tempered Clavier, Book II, B-flat minor - YouTube[/ame]
There are plenty of those block graph videos for Bach (and others) out there, here my favorite organ piece also in block graph display:
[ame="http://www.youtube.com/watch?v=ATbMw6X3T40"]Bach, Toccata and Fugue in D minor, organ - YouTube[/ame]
Seems hard to imagine that the first part (til 2:41 after which the fugue starts with presentation of the theme and following more or less the above mentioned course - with the exception that he here parts the theme later in two and even plays it at reverse instead of just upside down) was "improvised" during one sunday church service ("toccata" means "improvisation") and only after the fact written down by Bach and added to the most probably precomposed fugue.
Pure maths in the best baroque style and attitude, what a mastermind!
The interesting bit about all of this is that the human brain is either capable of following each voice seperately or listening to the overall tune (effect), but not both at the same time...
Enjoy (or not)!
Rattler