Luciano Berio retained an indelible childhood memory of seeing the Swiss-born Grock, a legendary circus clown of the time. Grock lived nearby, so that Berio was able to observe both his public and private personalities. That memory of Grock provided background inspiration for the fifth of the series of 14 Sequenzas, which stretched across Berio’s career as an ever-expanding work-in-progress. Each Sequenza focuses on a different solo instrument (including, in No. 3, the human voice). Stuart Dempster, an adventurous trombonist who was with the Oakland Symphony at the time, commissioned Sequenza V for his instrument in 1966.

Berio began the Sequenzas to work out issues of compositional language (a fact embedded in the title “Sequenza,” which refers to “a sequence of harmonic fields”). But he soon became absorbed by the opportunity to explore a given instrument as an all-encompassing phenomenon in itself rather than a mere vehicle to produce music. Berio’s curiosity extends from the cultural associations of an instrument to its unique physical properties and its relationship with the player.

All of these concerns merge in Sequenza V – along with an explicitly theatrical dimension that transforms traditional expectations of the recitalist-audience rapport into a brand of performance art. Berio’s score includes stage directions detailing the trombonist’s demeanor and actions. The piece consists of two unequal sections. In the first, broad vaudeville poses shine a garish light on the act and fact of performing. But Berio blurs the lines between performer and instrument: He anthropomorphizes the trombone, so that the player literally gives it voice by simultaneously vocalizing and blowing and thus producing a split personality, as if we were watching a ventriloquist’s routine. He reaches a point where (here Berio mimics a signature shtick of Grock’s) he is reduced to asking “Why?” (Jim Miller reinforces the Grock connection by wearing a clown costume at this performance.)

This showman’s performance seems at an end, but a longer, more “private” section follows in which the trombonist, seated, appears to be at work rehearsing; unbeknownst to him, we are now eavesdropping. Berio exploits the instrument’s flexibility (the cartoonish cliché of the “slide” trombone disrupts its noble tones) as the player seems to engage in a private dialogue with this mysteriously animated object, each trying to speak the other’s language.

Thomas May writes and lectures about music and theater.