From left: Alan Richardson, Nicholas Tavani, Rachel Shapiro and violist Gregory Luce make up the Aeolus Quartet.

Back in the late 1800s, if a musician couldn’t quite hack it on violin, he might get demoted to playing the instrument’s larger, deeper-voiced brother, the viola. But that’s long since ceased to be the case, says violist Michael Tree, a teacher at the Juilliard School in New York who will guest-star with the Aeolus Quartet at Strathmore on Thursday.

“Today the viola is taken seriously,” he says. “In fact, many of the leading conservatories consider it obligatory to study the viola if you are studying violin.”

Even when violists were maligned, composers knew that playing the instrument provided a unique vantage point for understanding the inner workings of a piece of music. That’s why many great composers, including Mozart and Beethoven, liked to play the viola part during private performances of their pieces.

Musicians, too, can benefit from the insider’s perspective the viola confers, Tree says. That’s why, in 1963, he left a promising career as a concert violinist to play viola in small ensembles. At Juilliard, Tree also coaches up-and-coming quartets, telling them to pay particular attention to the sounds in the middle of the musical spectrum — especially the viola, which has a rich, mellow voice compared to the violin’s bright lilt.

“Sometimes, the violist has to play louder than perhaps his colleagues would prefer,” Tree says.

That won’t be an issue Saturday, when Tree joins the Aeolus Quartet’s resident violist Gregory Luce in presenting Johannes Brahms’ “String Quintet in G Major.” The quintet adds an extra viola to the typical chamber-music lineup of two violins, a viola and a cello. Though the second viola adds depth, the G-major quintet is actually one of Brahms’ most cheerful pieces.

“Brahms said that the viola was his favorite string instrument,” Tree says. “He loved its dark, sonorous sound, so he must have thought that two violas are better than one.”

Viola? I Hardly Know Her! … and Other Jokes

How can you tell when a violist is playing out of tune? The bow is moving.

How do you keep your violin from getting stolen? Put it in a viola case.

How is lightning like a violist’s fingers? Neither one strikes in the same place twice. (Zing!)

Music Center at Strathmore, 5301 Tuckerman Lane, North Bethesda; Thu., 7:30 p.m., $28; 301-581-5100. (Grosvenor-Strathmore)