Evoking Harmony via Convolution
Sound
Summary
The authors explain a method to make any sound mimic the notes of a chord by mixing it with a special sound pattern made of many sinusoids, each tuned to a musical pitch. They use a tool called chord_convolver in Csound to do this mixing efficiently while avoiding unwanted noise. They compare their method with other common sound filters and show how it sounds using a recording from a field near an old castle. This approach helps transform ordinary sounds into ones with clear musical notes.
Authors
Michael Gogins
Abstract
I show how to evoke the pitch-class content of a chord from an arbitrary source sound by convolving the source with an impulse response whose grains are one windowed sinusoid per pitch-class, across each octave of hearing range; while, at the same time, minimizing artifacts. A Csound user-defined opcode, chord_convolver, mixes a dry Dirac component into that response, and applies partitioned convolution once. I contrast the effect with a linear-frequency comb filter and with a generic constant-Q resonator bank, and I demonstrate musical use on a twilight field recording alongside the ruins of Chateau de Lagarde.