"In 1937, R. R. Riesz demonstrated his mechanical talker which, like the other mechanical devices, was more reminiscent of a musical instrument. The device was shaped like the human vocal tract and constructed primarily of rubber and metal with playing keys similar to those found on a trumpet. The mechanical talking device ... produced fairly good speech with a trained operator ... With the ten control keys (or valves) operated simultaneously with two hands, the device could produce relatively articulate speech. Riesz had, through his use of the ten keys, allowed for control of almost every movable portion of the human vocal tract. Reports from that time stated that its most articulate speech was produced as it said the word 'cigarette'"
John P. Cater, "Electronically Speaking: Computer Speech Generation", Howard M. Sams & Co., 1983, p. 75.
The figure, above, shows Riesz's device.
"Air under pressure is brought from a reservoir at the right. Two valves, V1 and V2 control the flow. Valve V1 admits air to a chamber L1 in which a reed is fixed. The reed vibrates and interrupts the air flow much like vocal cords. A spring-loaded slider varies the effective length of the reed and changes its fundamental frequency. Unvoiced sounds are produced by admitting air through valve V2. The configuration of the vocal tract is varied by means of nine movable members representing the lips (1 and 2), teeth (3 and 4), tongue (5, 6 and 7), pharynx (8), and velar coupling (9).
To simplify the control, Riesz constructed the mechanical talker with finger keys to control the configuration, but with only one control each for lips and teeth (i.e., members 1-2 and 3-4 worked as pairs). The simplified arrangment with control keys is shown in the figure below. The dark surface regions indicate soft rubber linings to accomplish realistic closures and dampings. Keys 4 and 5 operate excitation valves V4 and V5, arranged somewhat differently from V1 and V2 in the figure above. Valve V4 admits air through a hole forward in the tract (below element 6) for producing unvoiced sounds. Valve V5 supplies air to the reed chamber for voiced excitation. In this case pitch is controlled by the amount of air passed by valve V5. When operated by a skilled person, the machine could be made to simulate connected speech."
James L. Flanagan, "Speech Analysis, Synthesis and Perception", Springer-Verlag, 1965, pp. 169-170.
Key controls of Riesz's mechanical talker.