[CM] mus-chebyshev-u-sum

[bil at ccrma.Stanford.EDU]

mus-chebyshev-u-sum takes a list of partial (harmonic)
amplitudes:

(with-sound (:srate 48000 :channels 1 :play #t)
   (let* ((dur 1.0)
	 (samps (seconds->samples dur))
	 (coeffs (float-vector 0 1 0 1/3 0 1/5 0 1/7 0 1/9))
	 (incr (hz->radians 200.0)))
     (do ((i 0 (+ i 1))
	 (x 0.0 (+ x incr)))
	((= i samps))
       (outa i (* 0.1 (mus-chebyshev-u-sum x coeffs))))))