To impose a vibrato (a periodic fluctuation of frequency) on the playback of a sound file, you can use a low-frequency oscillator (a cycle~ object) to modulate the playback speed of the file. The right inlet of the sfplay~ object controls the playback speed with a rate factor. A value of 1 is normal speed (the default), 2.0 is double speed, 0.5 is half speed, etc. The speed can be supplied as a constant number (float) or with a continuous signal.
Frequency modulation refers to using the output of a low-frequency oscillator to continually alter (modulate) the frequency of another oscillator. This example provides the user control of the amplitude and frequency of both the "carrier" oscillator (the one we hear directly) and the "modulator" oscillator (the effect of which we hear indirectly).
This program triggers a sound repeatedly, and changes the sound's playback rate with each repetition. The sound file is so short that there's really no need to turn it off with a 0, so we just start it with a 1. The playback rate is calculated so as to cause a random transposition from -12 to +12 equal-tempered semitones, using the twelfth root of 2; the number of semitones (x) of transposition is determined by setting the rate to "2 to the x/12 power". You can put the patch into Presentation mode, which will present a cleaner user interface.
To detect when an audio event (such as a musical note) occurs, one straightforward method is to test whether the peak amplitude of the audio signal surpasses an established threshold that's slightly above the level of the ambient noise floor. The peakamp~ object periodically reports the greatest absolute value of amplitude that has occurred during the specified time interval. For quick response, that interval should usually be every 10 to 30 milliseconds.
This patch shows a way to use the the abgate~ abstraction from the example "Routing a signal to one of two destinations" to route a signal through an audio effect processor, equivalent to using an effect insert in a mixer or a DAW. In order for this example to work correctly, you'll need to have that abstraction, saved with the name abgate~, in the Max file search path.
This patch is similar to the abgate~ abstraction for "Routing a signal to one of two destinations" with a fade from one to the other. However, instead of routing one input signal to one of two outlets, this abstraction permits you to choose one of two input signals to send out its lone outlet.
This patch is quite similar to the onoff~ abstraction for "Turning a signal on or off" with a fade-in or fade-out. Instead of just turning the signal on or off, though, this abstraction routes a signal to one of two outlets (with a fade from one to the other), which you can think of as destination A or destination B, based on whether the number in the right inlet is zero or non-zero.
To turn an audio signal on or off instantly, Max provides the gate~ object. However, if you use gate~ to switch a signal on or off while MSP is on, you're likely to cause an unwanted click due to the sudden discontinuity in signal amplitude.
Audio signals change drastically and quickly. A 100 Hz sine tone goes from (absolute value) peak to peak in 5 milliseconds. An attempt to detect its peak amplitude in a lesser time interval might incorrectly evaluate a non-peak values as a peak. What we really care about is the shape of the peaks over time, so a certain amount of latency is necessary to represent that shape properly. And, if we plan to use the envelope to shape other sounds, some smoothing of the envelope is necessary to minimize the audio-rate modulation it causes when applied to other signals.
This patch is very similar to the "Simple envelope follower", with the difference that in this patch the line~ object's time of interpolation to get to a detected peak value can be different from the peakamp~ object's interval of evaluation. If, for example, the peakamp~ interval is 10 ms and the line~ ramp time is 2.5 ms, the envelope follower latency will range from only 2.5 to 12.5 ms.