Thursday, February 19, 2009

The Rocks of Glacier Creek

Listen here: to this file

Subscribe here: to this RSS feed

This is a work in progress...

This is another take of this piece. It's scored for environmental sounds and a small ensemble of skilled microtonalists. The environmental sounds are recordings of a gentle waterfall and some birds typically found at the confluence of Glacier Creek and the Hoh River or thereabouts. The birds are the Hermit Thrush, the Black Throated Blue Warbler, the Stellar's Jay, the Hairy Woodpecker, the Pileated Woodpecker, and the Warbling Vireo.

The small ensemble of skilled microtonalists include clarinet, oboe, vibraphone, marimba, finger piano, cello, and harp. They are asked to accurately play the 53 TET scale, and also carefully slide up a set number of steps, for example, by 8 or 10 steps (approximating the ratios of 11:10 or 8:7 respectively). These guys are amazing in their flexibility and accuracy. I ask them to pick the chord inversion they want, and then slide up or down by a predetermined amount. My vibraphone player has perfected the art of bending his aluminum bars just the right amount to descend by a 6:7 (12 steps in 53-TET).

As always, this music is fake but accurate. Here is some of the coding for the sliding chords. The following is put through my Csound preprocessor to generate the necessary Csound code.

.slid-min3-u-a135 t+0&gls11:10. t+14&gls10:9. t+17&gls8:7.
.slid-min3-u-a351 o-1t+14&gls10:9. t+17&gls8:7. t+22&gls11:10.
.slid-min3-u-a513 o-1t+31&gls8:7. t+22&gls11:10. t+14&gls10:9.
.slid-min3-d-a531 o+1t+31&gls8:9. t-17&gls10:11. t-14&gls6:7.
.slid-min3-d-a153 o+1t+0&gls6:7. t-22&gls8:9. t-17&gls10:11.
.slid-min3-d-a315 t+14&gls10:11. t-14&gls6:7. t-22&gls8:9.
.slid-min3-u-b247 t+7&gls11:10. t+15&gls9:8. t+19&gls7:6.
.slid-min3-u-b472 o-1t+22&gls9:8. t+19&gls7:6. t+19&gls11:10.
.slid-min3-u-b724 o-1t+41&gls7:6. t+19&gls11:10. t+15&gls9:8.
.slid-min3-d-b274 o+1t+7&gls10:11. t-19&gls7:8. t-19&gls9:10.
.slid-min3-d-b427 o+1t+22&gls9:10. t-15&gls10:11. t-19&gls7:8.
.slid-min3-d-b742 t+41&gls7:8. t-19&gls9:10. t-15&gls10:11.

To call the chord, I just have to write code for each instrument, like this:

.mari-16-min-1f &mari.&key.e16w0d0h17&slid-min3-d-a*.d16
.mari-16-min-1g &mari.&key.e16w0d0h17&slid-min3-d-b*.d16

Then I call it when I want it to play like this:


The asterisk is a "don't care" character. This way, I can create several different note strings and let the computer pick the one it wants him to play at any given moment. Notice that the -a chords are the utonality triad to the 5 limit, and the -b are the higher overtones to the 11 limit. The chord slides from one to the other.

The &gls11:10. variables invoke a Csound function table that slides a note up or down over its duration by a very specific amount and timing. I basically multiply a note by a table of 256 values from 1 to a number larger or smaller than 1. Here is the relevant Csound code for a function table that slides a note to which it is applied by an 8:7. 8 divided by 7 is 1.14285714.

;f# step start at 1, stay there for 48 of the 256 steps
; move to 1.14285714 over 128 steps
; stay there for 80 of the 256 steps.
f324 0 256 -7 1 48 1 128 1.14285714 80 1.14285714 ; 8:7 g23 up 10

No comments: