(bind-func static atkrel_env_follow_c
  (lambda (atk:SAMPLE rel:SAMPLE)
    (let ((y1 0.0)
          (atkcoeff (/ 1000. (* atk (convert SAMPLE_RATE))))
          (relcoeff (/ 1000. (* rel (convert SAMPLE_RATE)))))
      (lambda (x)
        (set! y1 (+ x (* (if (> x y1) atkcoeff relcoeff) (- y1 x))))
        y1))))