Play a sound file with vibrato
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. So, you can supply a constant signal of 1 with a sig~ 1 object, and add to that a small offset up and down by means of a low-frequency low-amplitude sinusoidal oscillator (cycle~).