[CM] repeating envs

[bil at ccrma.Stanford.EDU]

I think you're close -- this slightly edited version
seems to work:

(define (strum e)
   (if (> (mus-location e) (mus-length e))
       (mus-reset e))
   (env e))

(with-sound (:srate 48000 :channels 1 :play #t)
   (let ((gen (make-polyshape 100.0 :partials (list 1 .5  2 .25  3 .125  
4 .125)))
	(strum-env (make-env '(0 0  .25  0.01  .5  0.2 1  0.0) :scaler 1.0 
:duration 1 :base .53))
         )
     (do ((i 0 (+ i 1)))
         ((= i 96000))
       (outa i (* .5 (polyshape gen 0.95 (strum strum-env))))
       )))

In your code, you had two things named "strum", and
the map-channel wasn't needed.