Datamath Calculator Museum:

"Texas Instruments invented around 1977 a novel approach to reproduce human speech with tuned voices stored in ROM's (Read Only Memory). The speech synthesis circuit duplicated the human vocal tract on a single piece of silicon and with the Speak & Spell in 1978 a new talking learning aid for children was introduced. Based on this technology a huge variety of speaking toys and educational games followed. The famous Speak & Spell toy and releated products attracted soon the artists of circuit-bending, a technique to modify electronic soundmaking toys and use them as an experimental musical instruments. "