lag i t

  i - input signal
  t - lag time

A simple averaging filter.

> import Sound.DF

> do { s <- sin_osc 0.05 0.0
>    ; let f = lin_lin s (-1.0) 1.0 220.0 440.0
>      in do { o <- sin_osc f 0.0
>            ; f' <- lag f 1.0
>            ; o' <- sin_osc f' 0.0
>            ; audition [] (out2 (o * 0.2, o' * 0.2)) } }