Palimpsest

Posted 13 May 2007, 10:58

Description

A meditation on remembrance, breath, stasis and change.

Duration: 10:58

Background & Technical Details

Palimpsest is the second in a series of works that began with Owllight (although it remains to be seen whether or not the series will continue). While the pieces have very different moods, they both employ cellular automata as a kind of structural template, and both are built from very simple materials: sine waves, some reverb, and very few notes.

Rule 57, width 68, height 100As in Owllight, the harmonic spectrum of every note is determined by the successive states of a simple one-dimensional cellular automaton (in this case, Rule 57) as shown on the right. The states start at the top of the image, with one state per row. A row consists of a series of “cells”, each of which is either “alive” (black) or “dead” (white). I treat each cell as a harmonic (i.e., an integral multiple of the base tone), so the more cells that are “alive”, the richer the sound. Each harmonic is made by an individual sine wave tone.

Palimpsest consists entirely of two two-note chords: 60Hz + 90hz (3/2, a just perfect fifth) and 67.5Hz + 90Hz (4/3, a just perfect fourth). Each chord proceeds through the series of spectral transformations represented by the diagram, but the chords are offset by the exact duration of a single state (the perfect fifth starts, and the perfect fourth follows), so that the chords alternate throughout the piece. In addition to the spectral changes, change occurs at two other levels. The length of the state (the “beat” of the piece) continually decreases at a slow rate, which provides an almost imperceptible sense of acceleration. Also, with every successive “beat”, the individual tones that make the harmonics are arpeggiated at a slightly greater rate, so that the chords get progressively more “smeared” over time; you can hear this most clearly on the very last chord in the piece.

This piece is dedicated to Carter Scholz, whose album Eight Pieces continues to inspire me. (Scholz co-wrote a very interesting sci-fi novel called Palimpsests that was published in 1984, but I had already named the piece before I remembered the book.)

Copyright & Licensing

Copyright © 2007, Dave Seidel. Some rights reserved. This work is licensed under a Creative Commons Attribution License.

Files/Downloads

MP3 (25MB, 48K/16-bit, 320kpbs)
OGG (20MB, 44.1K/16-bit, 221kbps)
blue & Csound project files (102KB)

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Owllight

Posted 10 April 2007, 10:58

Description

An ambient piece in a dark and mysterious mood.

Duration: 7 minutes.

Background & Technical Details

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 & Licensing

Copyright © 2007, Dave Seidel. Some rights reserved. This work is licensed under a Creative Commons Attribution License.

Files/Downloads

MP3 (16MB, 44.1K/16-bit, 320kpbs)
OGG (11MB, 44.1K/16-bit, 221kbps)
blue & Csound project files (39KB)

Tags

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