(TONEV-ALG
(NAME "tonev")
(ARGUMENTS ("sound_type" "s1") ("sound_type" "hz"))
(INLINE-INTERPOLATION T)
(INTERNAL-SCALING s1)
(ALWAYS-SCALE hz)
(START (MAX s1 hz))
(TERMINATE (MIN s1 hz))
(LOGICAL-STOP (MIN s1))
(STATE ("double" "scale1" "s1->scale")
       ("double" "c2" "0.0")
       ("double" "c1" "0.0")
       ("double" "prev" "0.0;
    hz->scale = (sample_type) (hz->scale * (PI2 / s1->sr))"))
(SAMPLE-RATE (MAX s1))
(STEP-FUNCTION hz)
(DEPENDS ("b" "hz" "2.0 - cos(hz)" TEMP "register double")
         ("c2" "hz" "b - sqrt((b * b) - 1.0)")
         ("c1" "hz" "(1.0 - c2) * scale1"))
(CONSTANT "c1" "c2" "b" "scale1")
(FORCE-INTO-REGISTER scale1)
(INNER-LOOP "            output = (sample_type) (prev = c1 * s1 + c2 * prev)")
)