diff --git a/code/thinkdsp.py b/code/thinkdsp.py
index 158f6430..aa62d8de 100644
--- a/code/thinkdsp.py
+++ b/code/thinkdsp.py
@@ -1948,7 +1948,7 @@ def main():
     sig3 = CosSignal(freq=660)
     sig4 = CosSignal(freq=880)
     sig5 = CosSignal(freq=987)
-    sig = sig1 + sig2 + sig3 + sig4
+    sig = sig1 + sig2 + sig3 + sig4 + sig5
 
     # wave = Wave(sig, duration=0.02)
     # wave.plot()