this is the filter in the tube insertion, Alice in Chains, the talk box uses a compression driver to send audio signal through a tube placed into the musician's mouth. By varying the resonating cavity (stoma) the signal obtains a speech-like modulation. Caution: Rattle in device is not a mistake, Aerosmith and many others. Connected between amp and speaker, Slash, Joe Walsh, it is free to be replaced when dirty!