I've got a DECtalk (DTC-01) I bought years ago on eBay, intending to use it for a speech recognition(!) project. It was state of the art when it was released - Dennis Klatt's speech synthesis research from the lab turned into a product.
What made DECTalk interesting is that it is a formant-based synthesizer, producing speech much like a human by taking a broad spectrum input voice source (cf. function of vocal cords) and modulating it via resonant frequencies (formants) similar to how we do it by changing the resonant frequencies of our vocal tract via articulation. When we recognize speech it's the frequency-tuned hairs in our inner ear acting as a filter bank and recognizing these resonant frequencies, which our brain has learnt to map back to the articulatory movements used to produce them.
Later, cheaper, and better sounding, speech synthesizers were based on stitching together partial recorded words (phonemes), which made them sound more natural but also limited them to speech. The DECTalk's more fundamental format-based generation allowed it to sing as well as talk, and the clean computer-generated formants made it highly intelligible (albeit artificial sounding) when sped up considerably, which was popular with the intended market of blind customers using it as a reading device.
What made DECTalk interesting is that it is a formant-based synthesizer, producing speech much like a human by taking a broad spectrum input voice source (cf. function of vocal cords) and modulating it via resonant frequencies (formants) similar to how we do it by changing the resonant frequencies of our vocal tract via articulation. When we recognize speech it's the frequency-tuned hairs in our inner ear acting as a filter bank and recognizing these resonant frequencies, which our brain has learnt to map back to the articulatory movements used to produce them.
Later, cheaper, and better sounding, speech synthesizers were based on stitching together partial recorded words (phonemes), which made them sound more natural but also limited them to speech. The DECTalk's more fundamental format-based generation allowed it to sing as well as talk, and the clean computer-generated formants made it highly intelligible (albeit artificial sounding) when sped up considerably, which was popular with the intended market of blind customers using it as a reading device.
Daisy, daisy, give me your answer, do ...