Matt Gilbert’s speech synthesizer let’s you recreate vocalsounds via touch interface -

Rather than typing or otherwise encoding text, the way you control speech with this synth is by imitating the shape made by a throat when speaking. When you lay your hand onto the controller, the tips of your fingers correspond to your mouth and your forearm corresponds to the back of your throat. The more you press down, the more you open that part of the throat. Currently, this synth can only control vowel sounds, but it does so fluidly; you don’t choose between one vowel or another, but you move fluidly between them through different gestures. This allows for more variation in inflection and emphasis.

For video, more info and other acoustic works see – Gestural speech synth

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Also from the same maker – Scrollbar Scarf – Updated Link