Pitch Keyboard Mod for a Speak and Spell

Pete from CasperElectronics has sent me this diagram explaining how to get a keyboard interface attached to the Speak and Spell for controlling the pitch. From the drawing it looks like the keys are pressing on tiny buttons allowing for resistance specified by the trimmer pots to be substituted. One thing to note is the fact that this device was build for Danny Elfman, the composer of Simpsons and other well known themes.