As you've heard, this machine says "coffee". It does so by breaking the word down into its basic speech sounds or "phonemes". All words are composed of phonemes—there are only about 40 of them in the English language. "Coffee" is made up of four of them, as shown below.
Since each phoneme is just a set of frequencies with a certain sequence, it can be made up electronically and fed into a speaker. Theoretically, if you had a machine with the 40 phonemes and you punched the buttons in the proper order, you could say anything you wanted.
Questions, accents, emphasis, etc., involve a frequency change over the whole word or sentence, which can be done electronically by adjusting the controls below. (By the way, since this unit was built in Holland, the machine says "coffee" with a definite Dutch accent.)