Corinna da Fonseca-Wollheim, Does Brahms’s Obsession With Rhythmic Instability Explain His Music’s Magic?, NYTimes, 19 October 2018:
A century separates the clarinet quintets of Mozart and Brahms, but at the emotional heart of each sits a slow movement of rapt, bucolic calm. In both, the strings play with mutes, creating a sound like a summer-morning haze, over which the clarinet drifts in unhurried legato lines. Brahms wrote his in 1891, after he had heard the Mozart quintet performed and grown infatuated with the clarinet’s sound.Listen closely to Brahms’s Adagio, and you may notice a destabilizing irregularity that is built into the rhythmic texture and lends it buoyancy and unease. Though the sound of the strings in the opening is misty, it is swirling with syncopations, overlapping cross-rhythms and hemiolas, rhythmic devices that dissolve a listener’s grounding sense of a first beat to the bar.You don’t have to be musically literate to know the bumpy feel of a cross-rhythm. Two-against-three can be a parent strolling hand in hand with a skipping child. Triplets on top of eighth notes are like a slow canter next to a trot: The two horses might move at the same speed, but you wouldn’t want them pulling a carriage together.Polyrhythms run through Brahms’s music like an obsessive-compulsive streak. In a bucolic moment such as the one in the Clarinet Quintet, which the Chamber Music Society of Lincoln Center performs on Nov. 15, they seem to subtly mirror the organic irregularity of nature.
A soul divided against itself?
That strategy of making emotions intense by juxtaposing opposites was inherently Romantic. The pianist and physicist Peter Pesic, whose fascinating book “Polyphonic Minds: Music of the Hemispheres” traces the role musical polyphony has played in man’s understanding of the mind, made that point in an interview. He said that 19th-century composers like Brahms were keen to exploit the expressive possibility of polyrhythms because they felt these represented something of the “intrinsic dividedness of the soul itself.”Like the protagonist of Goethe’s seminal “Faust,” “they believed that we have two souls in our breast,” Mr. Pesic said. “That thought was dear to the Romantics because it seemed to give a new depth to the feelings and emotions: They were not a single thing but a clash between different things.”Science, too, was then shifting to an understanding of the brain as not a single entity but as an organ comprising many subcenters. Pathologists examined the role of the brain’s two hemispheres in patients with mental illness; phrenologists tried to map mental faculties onto different areas.
I discuss polyrhythms in Chapter VI of Beethoven's Anvil (2001), pp. 116 ff. In a fragment I cut from the book I discuss the performance tips that, Joseph Hoffman, the 19th & 20th century virtuoso, offered in the pages of Ladies Home Journal. I've just posted this online:
3 Against 2: A Draft Fragment, https://www.academia.edu/37615907/3_Against_2_A_Draft_FragmentSee also, my post, Three Against Two the Tambuka Way.