BAIN MUSC 336 Introduction to Computer Music CHAPTER 4 The Synthesis of Sound by Computer “By using digital oscillators instead of actual physical devices, a computer can add up any number of simple sounds to create extremely complex waveforms.” – Burke et al., Music and Computers Terms & Concepts 4.1 Introduction to Sound Digital signal processing Vibrato Synthesis Filter theory Carrier Direct synthesis One sample delay Modulator Synthesis techniques FM index (fc/fm) Unpredictable information 4.4 Formant Synthesis Side bands Noise: White, Pink, etc. Formants (DFT) Bessel functions Synthesis function Resonant physical structure 4.8 Granular Synthesis 4.2 Additive Synthesis 4.5 Amplitude Modulation Grain Organ-stop analogy Amplitude modulation (AM) Grain envelope Telharmonium Tremolo Clouds Superposition of sinusoids Low frequency oscillator (LFO) Spectral envelope Signal block diagrams 4.9 Physical Modeling Common fate - Unit generator (ugen) Karplus-Strong algorithm Sine wave speech - f - Buffer (filled with noise) Shepard tones - a - Delay - Chroma - Waveshape - Feedback loop - Circularity of pitch Oscillator - Averaging - Carrier Feedback 4.3 Filters - Modulator Circular buffer Filter types (Fig. 4.8) Two-operator AM Virtual instrument - Low pass - High pass 4.6 Waveshaping Software - Band reject (notch) Transfer function Cycling ‘74’s MSP - Band pass Chebyshev Polynomials Puckette’s Pd - Comb - Order of the polynomial McCartney’s SuperCollider 3 Subtractive synthesis - Distortion index Vercoe’s Csound - Recursive formula Cutoff frequency Soft clipping Transition band Composers & Inventors Signal range Pass band Don Buchla & Robert Moog Stop band - Biopolar: –1 to 1 - Unipolar: 0 to 1 John Chowning Bandwidth Charles Dodge Center frequency Table-based waveshapes Buchla’s Touche Ken Gaburo Finite and infinite impulse Paul Lansky response filter (FIRF & IIRF) Algorithm - Optimization Larry Polansky Delays - Efficiency Jean-Claude Risset Averaging James Tenney Feedback 4.7 Frequency Modulation Barry Truax Unity gain transforms Frequency modulation (FM) Iannis Xenakis Reference Burk, Phil, Larry Polansky, Douglas Repetto, Mary Roberts and Dan Rockmore. 2011. Music and Computers: A Theoretical and Historical Approach, Archival Version. Available online at: <http://music.columbia.edu/cmc/MusicAndComputers/>. .