I wonder how many readers remember the original Palm Court of the Plaza Hotel in Manhattan. It was the place to have tea, while listening to a strolling trio of musicians, a string trio actually, consisting of violin, viola and cello. Maybe they didn’t stroll too much, with the cello and all, but I was, of course, too young to remember anything but the musicians close to my grandmother’s table.

Neither do I recollect what they played, but I assume their repertoire was heavy on Zdenko Fibich, Émile Waldteufel and the charming airs of Offenbach that soothe and settle so.

I started thinking about string trios because of the welcome inclusion of the pops trio, Simply Three, in this year’s Magic of Christmas series, with, among other numbers, a special rendition of “Carol of the Bells” for trio, chorus and the Portland Symphony Orchestra.

Why three musicians and not two, four or five? (Solos don’t count as chamber music. Don’t ask me why.) I thought it might have something to do with the Holy Trinity, but the ancient church, where what we call classical music originated, generally frowned upon instruments other than the organ.

The more mundane answer has to do with availability. In the 17th century there were few communities, even in Colonial America, without one or two violin players. Add some kind of bass continuo – harpsichord, cello, bass viol or guitar – and you had a versatile instrumental group, capable of playing the very popular works of Arcangelo Corelli or Luigi Boccherini, or serving up a minuet in the governor’s ballroom.

It was Joseph Haydn who gave the trio even more range and a sharper delineation of parts, by substituting a viola for one of the violins. The new grouping worked so well that it gradually displaced the older form in the way that the cello displaced the basso continuo of the harpsichord.

Earlier, of course, J.S. Bach had showed his virtuosity by writing trios for a single instrument, the organ or the harpsichord. His Sinfonias are written for three distinct voices but played with two hands, like a three-part fugue, but in a different form.

Haydn was also one of the first to write trios for piano, violin and cello, although the cello part often imitated that of the piano to strengthen its sound, which at the time was weak and tinkly. He must have liked the form, since he wrote 45 of them.

Mozart, in some of his later works in the form, made the piano one of three equal voices, a tradition carried on by Beethoven as the piano sound grew ever stronger. Eventually it became so dominating that some trios sound like piano concertos with string accompaniment. (Not that there’s anything wrong with that.)

A huge number of trios, both string and piano, have been written over the years, some better than others, but a good place to start would be Beethoven’s “Archduke” Trio (Opus 97). By that time, the trio form was so popular that Beethoven even transcribed two of his symphonies for it.

In the 20th century, the trio format became popular among jazz musicians, using a wide variety of instruments. Benny Goodman used the form in the 1930s, and rock groups picked it up with the advent of the “power trio,” consisting of guitar, bass and drums, with one or more of the musicians also singing vocals. There are even rap trios, or so I am told, such as The Beastie Boys.

Simply Three has returned to the roots of the string trio, but heavier on the lower end of the register, with violin, cello and bass, sometimes with added percussion. They’re not quite subdued enough for the newly renovated Palm Court, even though it has, horrible to relate, a little circular bar in the middle of the floor. I used to have to go down to the Oyster Bar for a black velvet, made with Guinness stout and champagne.

Christopher Hyde is a writer and musician who lives in Pownal. He can be reached at:

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