Tutorials and Topics - Peabody Computer Music

Tutorial 7: Synthesis—Additive synthesisIn the tutorial examples up to this point we have synthesized sound using basicwaveforms. In the next few chapters we’ll explore a few other well known synthesistechniques using sinusoidal waves. Most of these techniques are derived from precomputeranalog synthesis methods, but they are nevertheless instructive and useful.Combining tonesA sine wave contains energy at a single frequency. Since complex tones, by definition, arecomposed of energy at several (or many) different frequencies, one obvious way tosynthesize complex tones is to use multiple sine wave oscillators and add them together.Four sinusoids added together to make a complex toneOf course, you can add any waveforms together to produce a composite tone, but we’llstick with sine waves in this tutorial example. Synthesizing complex tones by adding sinewaves is a somewhat tedious method, but it does give complete control over theamplitude and frequency of each component (partial) of the complex tone.In the tutorial patch, we add together six cosine oscillators (cycle~ objects), withindependent control over the frequency, amplitude, and phase of each one. In order tosimplify the patch, we designed a subpatch called partial~ which allows us to specify thefrequency of each partial as a ratio relative to a fundamental frequency.The contents of the subpatch partial~For example, if we want a partial to have a frequency twice that of the fundamental wejust type in 2.0 as an argument (or send it in the second inlet). This way, if several partial~objects are receiving their fundamental frequency value (in the left inlet) from the same99