The Generator is a mechanism to produce sound , which is required for speech.

The purpose of respiration for speech, is to move air. Of course there are other muscles not involved with moving air which must nevertheless be coordinated with the breath stream.

These are the muscles of the soft palate (velum), the tongue, lips jaw, and the larynx. The function of the larynx, of course, is to generate the sounds for the vowels and many consonants.

Generator: The whole purpose of moving air is to create sound which can transmit a symbolic signal. There are a number of locations around the body, and particularly in the oral track were sounds can be made. Tapping with the feet is one example. "Donald Duck" talk using the back of the oral cavity is another. Using the feet takes considerable energy, and it's hard to find a time when the feet are not precoccupied with walking or standing.