Sounds previously considered illusions have turned out to exist. “A musical sound once thought to be heard only in our heads as a quirk of the ear canal is actually real,” writes Karmela Padavic-Callaghan at the New Scientist. “Violins can produce these unusual tones – and higher quality violins can produce them more strongly.” Padavic-Callaghan explains that questions about this third tone — eventually called a “combination tone” — date back over 300 years, to a discovery in 1714 by Giuseppe Tartini (1692-1770), a Baroque-era Italian violinist and composer.
A newly published article in The Journal of the Acoustical Society of America is the source of the New Scientist piece. Interestingly, in the work of the scientists exploring the subject, it turned out that older instruments produced more prominent third notes.
To put this discovery (credited to Gabriele Caselli, Giovanni Cecchi, and Giulio Masetti) in context, a distinction has now been made between what we experience as heard versus what is actually present in the world. It would be one thing if the sound exists only because of how our ears are structured (“It was thought that these tones arose entirely in our ears, due to the way sound is amplified by the cochlea, rather than actually emanating from an instrument”). In contrast, the violins actually produce this previously mysterious sound. The discovery both upends a long-held misapprehension, and potentially opens up compositional techniques for composers who wish to exploit this sonic phenomenon. (Thanks, Glenn Sogge!)