Origin of trichords in pianos

[Robert L. Simmen]

I am writing an article on piano tuning, and in my research I have not been able to find definitive source of the three strings per key of the pianoforte. When and why was it done? Surely there is more to it than merely greater volume? Can anyone refer me to an authoritative source? The great article in Britannica doesn't tell why.

[Bill Kibby]

I think I already established in response to your last posting that volume is not the issue. As with so many things in life, I can't imagine that there was ever a single, simple reason: Trichords sound much better than bichords in many ways, but experience showed piano makers that more than three strings didn't really achieve much improvement, so three is the optimum. Once we complete the re-organisation of our office, some more definite news may appear about the earliest-known use of trichords. Why not email me?

[Bill Kibby]

I'm grateful to Kenneth Mobbs, who tells me that...

"Broadwood grands from 1788 are trichord.

German/Austrian: the Stein 1784 that Hubbard copied is bichord to d2
sharp and then trichord to the top f3.

Even as late as 1815 or so Fritz was using bichord for three octaves FF to e1 and trichord from f1 to top f4"

[Tom Tuner]

Although trichords are not half again as loud as bichords, they sustain longer. One article in Science magazine some years back was a discussion of how the slight phase differences among three strings (which amount to slight differences in tuning) cause them to transfer energy among themselves. It is a commonplace that out-of-tune unisons actually sound louder the perfectly clean ones.

[Bill Kibby]

The short answer is that trichords were in occasional use in harpsichords and clavichords before pianos existed, and we know that by the 1770s, some grands had trichords in the treble, probably an attempt to strengthen the notes on those very short strings.