by Jonah Lehrer

When most people think about musical improvisation, they imagine Charlie Parker and John Coltrane, inventing melodies in smoky jazz clubs. But the act of musical improv isn't a 20th century invention. As Alex Ross notes in this fascinating article, "classical" music has long reserved a spot for improvisation by the performer. The cadenza, a spot at the end of the piece reserved for a display of virtuosity, was designed to encourage improvisation, as soloists figured out, on the fly, how to finish off a Mozart concerto:

Cadenzas sprang up in the early eighteenth century, when composers began indicating brief episodes where the performer should play freely, delaying a final cadence. They appeared not only in opera but also in instrumental pieces, especially in the closing sections of concerto movements. Musicians had been embellishing the score for centuries, and perhaps the cadenza was a way of bringing improvisation under control, corralling it. Mozart, as composer and pianist, brought the practice to its peak; one of his contemporaries stated that cadenzas should be dreamlike in their logic, expressing “ordered disorder,” and Mozart’s playing evidently had that quality. (He wrote out cadenzas for many of his concertos, so his performances may not always have been spontaneous.) Beethoven carried on the traditionthe darkly rumbling cadenza that he devised for Mozart’s D-minor Piano Concerto is a fascinating case of one composer meditating on anotherbut he also helped to kill it. In the first movement of the “Emperor” Concerto, the soloist is told not to make a cadenza but to play “the following”a fully notated solo. Performers gradually stopped working out their own cadenzas, instead turning to a repertory of written-out versions. Opera singers retained more freedom, especially when it came to interpolating bravura high notes, but they, too, grew more cautious. Improvisation became the province of church organists and avant-gardists, the latter often taking inspiration from jazz

In recent years, there have been several interesting neuroscience experiments that attempt to get inside the head of performers as they engage in improv. One study, led by Charles Limb of the NIH and Johns Hopkins University, examined the brain activity of jazz musicians as they played on a piano. The musicians began with pieces that required no imagination, such as the C-major scale and a simple blues tune they’d memorized in advance. But then came the creativity condition: The musicians were told to improvise a new melody as they played alongside a recorded jazz quartet.

While the musicians riffed on the piano, giant magnets whirred overhead monitoring minor shifts in their brain activity. The researchers found that jazz improv relied on a carefully choreographed set of mental events, which allowed the musicians to discover their new melodies. Before a single note was played, the pianists exhibited a “deactivation” of the dorsolateral prefrontal cortex (DLPFC), a brain area associated with planned actions and self-control. In other words, they were inhibiting their inhibitions, which allowed the musicians to create without worrying about what they were creating.

But it’s not enough to just unleash the mindsuccessful improv requires a very particular kind of expression. That’s why the fMRI machine also recorded a spike in activity in the medial prefrontal cortex, a fold of frontal lobe just behind the eyes. This area is often linked with self-expressionit lights up, for instance, whenever people tell a story in which they’re the main character. The scientists argue that this part of the brain is required for jazz improv because the musicians are channeling their artistic identity, searching for the notes that best summarize their style.

As Ross notes, this unique mental mode has a long and distinguished tradition within classic music and opera. I have a feeling Mozart would have enjoyed Miles Davis.