Aurora (for Kraig Grady)
Posted 10 April 2007, 17:58
An ambient piece in a dark and mysterious mood.
Duration: 7 minutes.
I first encountered the word “owllight” (in hyphenated form) in the Dylan Thomas poem Altarwise by owl-light, which I first read as a teenager. The word hadn’t occurred to me in many years, but as I worked on this piece and searched for a title, I remembered the term and it felt right. I looked it up online and found a great definition from Webster’s 1913 dictionary: “glimmering or imperfect light”. The piece has, to my ears, a somewhat somber, mysterious, and possibly foreboding mood, which seems appropriate given the place the owl occupies in folklore. I’m also reminded of the creepy owls in Twin Peaks, which were apparently based on aspects of Native American mythology. (“The owls are not what they seem.”)
The technical notes that follow may be irrelevant to your experience of listening to the piece, but I present them (as I generally do) in case someone is curious about the compositional process I followed.
This piece is made by varying the harmonic spectra of three tones at 60Hz, 90Hz, and 97.08Hz, which we hear as root (1/1, at stereo center), perfect fifth (3/2 or 1.5/1, at stereo left), and sharp or augmented fifth (1.618/1, which is an approximation of the golden ratio, at stereo right). The ~7Hz difference between the second and third pitches produces a binaural beating effect in the approximate range of the transition between alpha and theta waves. If you listen carefully, you will hear this three-note phrase repeating throughout the piece.
The structure of the piece is governed by the first 97 states of a 1-dimensional cellular automaton known as Rule 150. I treat the center cell in each state as the fundamental and the cells on either side as harmonics (odd-numbered on one side, even-numbered on the other side).
I wrote this using Steven Yi’s fantastic program blue, which is a front end for Csound. This is the first time I used the blue feature that allows one to generate the Csound score from Python code. The code that calculates cellular automata is based on a Python Cookbook entry by Rick Muller. The sounds themselves are entirely made up of individually-generated sine waves with some reverb; I used no other waveforms or effects of any kind.
Copyright © 2007, Dave Seidel. Some rights reserved. This work is licensed under a Creative Commons Attribution License.