rand :: Fractional a => Pattern a
rand generates a pattern of (pseudo-)random, floating point numbers between 0 and 1. For example to randomly pan around the stereo field you can:
d1 $ sound "bd*8" # pan rand
Or to enjoy a randomised speed from 0.5 to 1.5, you can add 0.5 to it.
d1 $ sound "arpy*4" # speed (rand + 0.5)
irand :: Num a => Int -> Pattern a
irand is similar to rand, but generates a pattern of (pseudo-)random integers between 0 to n-1 inclusive. Notably used to pick random samples from a folder.
d1 $ sound "amencutup*8" # n (irand 8)