The "chorus" effect is commonly used to enrich a sound. The effect gets its name from the way that a chorus of people singing or speaking in unison sounds different from a single person. By extension, a group of violins sounds different from a single violin (even though we don't call a violin section a "chorus"), and the same effect even takes place inside a piano because most of the hammers strike two or three strings tuned in unison rather than a single string.
For this example to work properly, you will also need to download the additional Max file mix~.maxpat from the example “A use subpatch for mixing and balancing two sounds.”
If you want to make an oscillator with unstable pitch, you can modulate the pitch of the oscillator using a noise signal as an exponent with a base of 2, and applying that as a multiplier to vary the fundamental frequency. In that way, when the noise ranges from -1 to +1, it will cause a pitch variation of ±1 octave, whatever the fundamental frequency of the oscillator. Divide the amplitude of the noise by 1200 if you want to be able to represent pitch variation in cents.