Tartini, the third tone and the cochlea

"It is physically certain that given two simultaneous loud and prolonged tones one can hear a third tone, different from the played sounds": with these words taken from his essay Trattato di musica secondo la vera scienza dell'armonia published in 1754 Giuseppe Tartini (1692-1770), celebrated violinist, and researcher of musical theory and "physicomathematical harmonist" (Barbieri, 1990) introduces his discovery, made some years before (in 1713), of the socalled third tone. As explained by Tartini himself, if a listener stands halfway between two violin or oboe players some steps apart, he can hear another tone, in addition to the played notes (principal or primary notes), called by Tartini the "third tone"