MIDI stream to exponential curve

In this patch the zmap object changes the scale of the incoming number stream from the ctlin object from the standard range of MIDI (0-127) – the 0 is bypassed so that it is translated properly once the range is mapped back to linear amplitude – to a specified range in decibels – in the case of the example from -63 to 0 dB.

Using matrix~ for audio routing and mixing

The matrix~ object is an audio mixer/router that can be configured with any number of inlets and outlets. The arguments specify the number of audio inlets, the number of audio outlets (there's always one additional outlet on the right), and the initial gain for the connections of inlets to outlets. Each inlet is potentially connectable to each outlet with a unique gain setting. The gain of the connections is changed by sending messages in the left inlet.

Simple wavetable synthesis

One of the earliest methods of digital sound synthesis was a digital version of the electronic oscillator, which was the most common sound generator in analog synthesizers. The method used was simply to read repeatedly, at the established sample rate, through a stored array of samples that represent one cycle of the desired sound wave. By changing the step size with which one increments through the stored wavetable, one can alter the number of cycles one completes per second, which will determine the perceived fundamental frequency of the resulting tone.

Windowing an audio signal

In signal processing, a "window" is a function (shape) that is nonzero for some period of time, and zero before and after that period. When multiplied by another signal, it produces an output of 0 except during the nonzero portion of the window, when it exposes the other signal. The simplest example is a rectangular window, which is 0, then briefly is 1, then reverts to 0. The windowed signal will be audible only when it is being multiplied by 1––i.e., during the time when the rectangular windowing occurs.

Polyphony requires multiple objects

Any given MSP patch cord represents a single channel of audio. If you want to generate or process multiple sounds or channels, you need to treat each sound or channel separately. For example, each sfplay~ object can have multiple loaded sound cues so that it's ready to play any one of several files, but it can only play one sound file at any given instant. And if it's a stereo file you need to treat each channel separately for mixing, processing, etc. This patch demonstrates that.