Update audio processing state: next_index=21

processing_audio_state.json

@@ -17,6 +17,7 @@
     "audio/week07 03 one way of building a muscle pt1.wav": "processed",
     "audio/week07 02 looking at reference.wav": "processed",
     "audio/week07 01 intro what do muscles do.wav": "processed",
-    "audio/week06 14 building a low res cage pt2.wav": "processed"
+    "audio/week06 14 building a low res cage pt2.wav": "processed",
+    "audio/week06 13 building a low res cage pt1.wav": "processing"
   }
 }