“Machinatuosity”: Virtual Strings, Spectral Filters and Temperament Tools for Esquisse

Abstract

This paper describes the technological component under- pinning the author’s composition ‘Esquisse (in Memoriam J.-C. Risset)’, for piano and computer, in the form of real- time signal processing and synthesis implemented in the Max visual programming language. The computer part, designed specifically for this piece, incorporates some novel techniques, including an extension of the Karplus- Strong algorithm that permits the synthesis of string har- monics via one simple control parameter, and a spectral- domain filtering system based on comb-like harmonic filters which also incorporate spectral-domain bandpass “windows” the can be calculated on either a linear fre- quency or octave scale. The practical result of this is the ability to create harmonic filters representing a single formant of any size or full-spectrum harmonic filters whose fundamental changes in different parts of the spec- trum. The piece also incorporates some specially de- signed tuning tools to reconcile the equal-tempered tun- ing of the piano with the use of the harmonic series in the electronics as a prevalent compositional device used throughout the piece.