If the vocoder is being used with a microphone double check that the input sensitivity has been switched from "LIN" (Line Level, the factory default) to "MIC". This is the correct sensitivity for a microphone or for a guitar. Next, adjust the audio input trim for the best signal level. Dial-up one of the vocoder presets - 259, 269 or 279 - and play notes on the K-Station at the same time as talking or singing into the mic. The vocoder effect should be audible. For more information on the input sensitivity and input trim see page 36 in the K-Station manual.