;; (arc-cos a)

;; Arc cosine.

(let* ((a (line kr -1 1 1 remove-synth))
       (b (sub (fdiv (arc-cos a) (/ pi 2)) 1))
       (f (mul-add b 900 1600)))
  (audition 
   (out 0 (mul (sin-osc ar f 0) 0.1))))