I’m trying to use the vocoder effect but it doesn’t work.

I’m on Windows 10, using Audacity v. 2.2.2

I tried following a tutorial: I imported a voice file and made it the left channel, and put a sawtooth tone in the right channel. Then I combined them into a stereo track, then I higlighted it and tried running the Vocoder effect with various parameters.

When I run it the tracks are unchanged. When I check the debug window it says:

```
error: (a2 <= -1) or (1 - a2 <= |a1|) (unstable parameters a1 = -1.99997, a2 = -1.00089) in biquad
Function: #<Subr-ERROR: #edd88f0>
Arguments:
"(a2 <= -1) or (1 - a2 <= |a1|) (unstable parameters a1 = -1.99997, a2 = -1.00089) in biquad\n"
Function: #<FSubr-IF: #edda320>
Arguments:
(OR (<= A2 -1) (<= (- 1 A2) (ABS A1)))
(ERROR (FORMAT NIL "(a2 <= -1) or (1 - a2 <= |a1|) (~A a1 = ~A, a2 = ~A) in biquad~%" "unstable parameters" A1 A2))
Function: #<FSubr-LET: #edd5a40>
Arguments:
((A0R (/ 1 A0)))
(SETF A1 (* A0R A1) A2 (* A0R A2))
(IF (OR (<= A2 -1) (<= (- 1 A2) (ABS A1))) (ERROR (FORMAT NIL "(a2 <= -1) or (1 - a2 <= |a1|) (~A a1 = ~A, a2 = ~A) in biquad~%" "unstable parameters" A1 A2)))
(SND-BIQUAD X (* A0R B0) (* A0R B1) (* A0R B2) A1 A2 0 0)
Function: #<Closure-NYQ:BIQUAD: #ec34fd0>
Arguments:
#<Sound: #9c1f4b8>
-0.000447076
0
0.000447076
0.999553
-1.99907
-1.00045
Function: #<Closure-NYQ:BIQUAD-M: #ec34890>
Arguments:
#<Sound: #9c1f4b8>
-0.000447076
0
0.000447076
0.999553
1.99907
1.00045
Function: #<FSubr-LET*: #edd8330>
Arguments:
((W (* 2 PI (/ HZ (SND-SRATE X)))) (CW (COS W)) (SW (SIN W)) (ALPHA (* SW (SINH (/ 0.5 Q)))) (A0 (+ 1 ALPHA)) (A1 (* -2 CW)) (A2 (- 1 ALPHA)) (B0 ALPHA) (B1 0) (B2 (- ALPHA)))
(NYQ:BIQUAD-M X B0 B1 B2 A0 A1 A2)
Function: #<Closure-NYQ:BANDPASS2: #ec32610>
Arguments:
#<Sound: #9c1f4b8>
8077.56
34.0577
Function: #<Subr-APPLY: #edd7040>
Arguments:
#<Closure-NYQ:BANDPASS2: #ec32610>
(#<Sound: #9c1f4b8> 8077.56 34.0577)
Function: #<FSubr-SETF: #edd5860>
Arguments:
(AREF RESULT I)
(APPLY FN (MAPCAR (FUNCTION (LAMBDA (A) (COND ((ARRAYP A) (AREF A I)) (T A)))) ARGS))
Function: #<FSubr-DOTIMES: #edd9280>
Arguments:
(I LEN)
(SETF (AREF RESULT I) (APPLY FN (MAPCAR (FUNCTION (LAMBDA (A) (COND ((ARRAYP A) (AREF A I)) (T A)))) ARGS)))
Function: #<FSubr-COND: #edd8990>
Arguments:
(LEN (SETF RESULT (MAKE-ARRAY LEN)) (DOTIMES (I LEN) (SETF (AREF RESULT I) (APPLY FN (MAPCAR (FUNCTION (LAMBDA (A) (COND ((ARRAYP A) (AREF A I)) (T A)))) ARGS)))) RESULT)
(T (APPLY FN ARGS))
Function: #<FSubr-LET: #edd5a40>
Arguments:
(LEN NEWLEN RESULT)
(DOLIST (A ARGS) (COND ((ARRAYP A) (SETF NEWLEN (LENGTH A)) (COND ((AND LEN (/= LEN NEWLEN)) (ERROR (FORMAT NIL "In ~A, two arguments are vectors of differing length." FN)))) (SETF LEN NEWLEN))))
(COND (LEN (SETF RESULT (MAKE-ARRAY LEN)) (DOTIMES (I LEN) (SETF (AREF RESULT I) (APPLY FN (MAPCAR (FUNCTION (LAMBDA (A) (COND ((ARRAYP A) (AREF A I)) (T A)))) ARGS)))) RESULT) (T (APPLY FN ARGS)))
Function: #<Closure-MULTICHAN-EXPAND: #ebc3d00>
Arguments:
#<Closure-NYQ:BANDPASS2: #ec32610>
#(#<Sound: #9c1f4b8> #<Sound: #9c197c0>)
8077.56
34.0577
Function: #<Closure-BANDPASS2: #ec32d70>
Arguments:
#(#<Sound: #9c1f4b8> #<Sound: #9c197c0>)
8077.56
34.0577
Function: #<FSubr-SETF: #edd5860>
Arguments:
BAND
(BANDPASS2 S F Q)
Function: #<FSubr-DO*: #edd6f90>
Arguments:
((I 0 (1+ I)) MOD-ENVELOPE BAND (RESULT 0) (Q (/ (SQRT 2) (/ OCTAVES BANDS))) (P (+ (HZ-TO-STEP 20) (/ INTERVAL 2)) (+ P INTERVAL)) (F (STEP-TO-HZ P) (STEP-TO-HZ P)))
((= I BANDS) RESULT)
(SETF BAND (BANDPASS2 S F Q))
(SETF MOD-ENVELOPE (LOWPASS8 (S-ABS (AREF BAND 0)) (/ F DST)))
(SETF RESULT (SUM RESULT (BANDPASS2 (MULT MOD-ENVELOPE (AREF BAND 1)) F Q)))
Function: #<Closure-VOCODER: #ed69c68>
Function: #<FSubr-SETF: #edd5860>
Arguments:
S
(VOCODER)
Function: #<FSubr-LET: #edd5a40>
Arguments:
((ORIGINAL (OR (= MST 0) (AREF S 0))))
(SETF S (VOCODER))
(SETF S (SCALE (/ (PEAK S NY:ALL)) S))
(CASE MST (0 S) (1 (VECTOR ORIGINAL S)))
Function: #<FSubr-COND: #edd8990>
Arguments:
((ARRAYP S) (MIX) (LET ((ORIGINAL (OR (= MST 0) (AREF S 0)))) (SETF S (VOCODER)) (SETF S (SCALE (/ (PEAK S NY:ALL)) S)) (CASE MST (0 S) (1 (VECTOR ORIGINAL S)))))
(T "Error.\nStereo track required.")
1>
```

Thanks.