Comb filtering could be added to the Nyquist code with either of these commands:
(scale 0.6 (sim (mult s (hzosc 35))(at-abs 0.003 (cue (mult s (hzosc 35))))))
(comb (mult s (hzosc 35)) 0.1 150)
The first example does exactly as Trebor describes and mixes the processed sound with a copy that is delayed by 3 milliseconds.
The second example uses a comb filter effect where the last number (150) is the filter frequency in Hz and the second to last number (0.1) is the decay time of the resonance in seconds.