(define bass
(lambda (beat ps ds)
(play fmsynth (- (car ps) 12) (cosr 90 40 7/3) (* .6 (car ds))
(trir 0.0 2.0 5/3) 0.5)
(callback (*metro* (+ beat (* .5 (car ds)))) 'bass (+ beat (car ds))
(rotate ps -1)
(rotate ds -1))))