Real-Time Polyphonic Octave Doubling for the Guitar

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Journal Title
Journal ISSN
Volume Title
Sähkötekniikan korkeakoulu | Master's thesis
Date
2016-04-04
Department
Major/Subject
Acoustics and Audio Signal Processing
Mcode
S3004
Degree programme
TLT - Master’s Programme in Communications Ecosystem (TS2005)
Language
en
Pages
66+7
Series
Abstract
This thesis studies digital signal processing solutions for enriching live guitar sound by way of mixing-in octave-doubled versions of the chords and melodies performed on the instrument in real-time. Following a review of techniques applicable for real-time polyphonic octave doubling, four candidate solutions are proposed, amongst which two novel methods: ERB-PS2 and ERB-SSM2. Performance of said candidates is compared to that of three state of the art effect pedal offerings of the market. In particular, an evaluation of the added roughness and transient alterations introduced by each solution in the output sound is conducted. The ERB-PS2 method, which consists in doubling the instantaneous phases of the sub-bands signals extracted with a constant-ERB-bandwidth non-decimated IIR filter bank, is found to provide the best overall performance amongst the candidates. This novel solution provides greatly reduced latency compared to the baseline pedals, with comparable, and in some case improved, sound quality.
Description
Supervisor
Välimäki, Vesa
Thesis advisor
Kargo, Jens Peter
Arknaes, Lars
Keywords
real-time, pitch-shifting, multi-resolution, sub-band, modulation, roughness
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Citation