Poster for the Mainly Mozart Festival.

This Sunday, the 20th incarnation of South Florida’s Mainly Mozart Festival launches at the Coral Gables Museum, and will last over the next six weekends. As the festival’s title suggests, the music of Mozart is a central focus, and will be featured in each of the concerts. But there will also be a good deal of other music, and with a decidedly 20th-century twist.

Cellist Aaron Merritt, who is coordinating the concerts, said the four area string quartets that have appeared at previous festivals — the Amernet, Bergonzi, Delray and Sona quartets — will be returning this year, but the quartet-centric focus of the previous festivals will be leavened with solo sonatas, piano trios and the pioneering Clarinet Quintet of Mozart.

“It’s easy to forget that Mozart wrote such amazing music for wind instruments, including the concerti and the Horn Quintet. The Clarinet Quintet is one of his best pieces of chamber music,” he said, and is scheduled for June 9, when clarinetist Margaret Donaghue Flavin will perform it with the Bergonzi Quartet, resident foursome at the University of Miami.

The Sona String Quartet.

Another special feature of the festival will be the Sona Quartet’s performance of Three Divertimenti, an early work by Benjamin Britten, whose birth centenary is being observed in the classical music world this year. Although Britten is primarily remembered for his contribution to British opera, he also wrote a good deal of instrumental and chamber music, including three string quartets.

The Three Divertimenti, premiered in 1936, is a revision of an early string quartet Britten began writing while in his teens and studying with composer Frank Bridge.

“It’s kind of like a student piece, but it’s already pretty advanced and pretty interesting,” said Merritt, who is the cellist in the Sona Quartet, formed for the Miami Music Project. He said the Britten will contrast nicely with the other works on the program, Mozart’s Quartet No. 14 (in G, K. 387) and the big F minor Piano Quintet of Brahms (Op. 34), with the Ukranian-born pianist Marina Radiushina.

The Bergonzi String Quartet.

Another unusual offering will be the late String Quartet (Voces Intimae, Op. 56) of Jean Sibelius, set for performance by the Bergonzi Quartet on the June 9 concert that includes the Mozart Clarinet Quintet.

“I love Sibelius; I’m constantly going through his music. It’s what I call a perpetual Sibelius cycle,” he said. “You hear the symphonies, and the big, sweeping orchestral tone poems, but you never hear him small-scale.” The quartet, which dates from 1909, is Sibelius’ only mature work of chamber music, though there are two earlier string quartets that were unpublished during his lifetime.

The Delray String Quartet.

The Delray String Quartet, fresh off a recording session featuring the Piano Quintet of Cesar Franck, will bring pianist Tao Lin along to perform that work on May 18. Quartet violist Richard Fleischman will be featured in a quartet by Mozart’s contemporary, Franz Anton Hoffmeister, written for viola d’amore.

That will be paired with the so-called Hoffmeister Quartet of Mozart (No. 20 in D, K. 499), which Hoffmeister, who also was a music publisher, commissioned from Mozart in 1786. “Mozart and Hoffmeister were very close,”Merritt said. “The first half of the program will be these two contemporaneous, similar-ish pieces.”

The festival opens Sunday with the Amernet String Quartet, one of Miami’s most familiar chamber groups; the foursome will appear twice during the festival. The centerpiece of Sunday’s concert will be a string sextet, Tchaikovsky’s lovely Souvenir de Florence (Op. 70), in which Merritt will play the second cello part and violist Yael Kleinman Hyken will play second viola. They’ll also perform a Mozart rarity, the String Quartet No. 8 (in F, K. 168), written when Mozart was just 17 years old.

The Amernet String Quartet.

“With all these quartets playing all the time, we get a lot of the late quartets of Mozart. So it’s nice that they’re going to offer an early, shorter Mozart quartet,” he said. The program also includes the infrequently programmed String Quartet No. 2 (in D-flat, Op. 15) of the Hungarian pianist and pedagogue Ernst von Dohnanyi, who taught at Florida State in later years, and whose music seems to be enjoying something of a revival, particularly with chamber groups.

The Amernet Quartet returns May 26 with pianist Paul Posnak in the Piano Quartet No. 1 (in G minor, K. 478) of Mozart, a pioneering work in that form. Tchaikovsky’s String Quartet No. 1 (in D, Op. 11) and the Italian Serenade of the Austrian lieder composer Hugo Wolf round out the concert.

Longtime UM professor and musicologist Frank Cooper, who founded the festival 20 years ago, will be on hand during the final concert June 16 (the only concert to be held at UM’s Gusman Hall) to discuss the widely varied program, which has been assembled by Radiushina.

Marina Radiushina.

“She’ll have some really interesting pieces on there that you normally don’t hear down here in Miami,” Merritt said, including the Violin Sonata of Leos Janacek, excerpts from the Cello Sonata No. 1 of Alfred Schnittke, and the piano trio version of Astor Piazzolla’s Four Seasons of Buenos Aires, along with music by Manuel de Falla, Arvo Pärt and the Piano Trio No. 10 (in C, K. 548) of Mozart.

Two free children’s concerts are part of the festival as well: a “String Fling” with the Sona Quartet on the afternoon of May 25, and “All You Need Is Brass,” on June 8, featuring the Miami Music Project Brass Quintet.

Merritt said the programming for the festival has broadened to include newer music over the years, but it has always been a series designed to showcase area musicians.

”It’s good to have the focus on Mozart but also have the diversity of other compositions, and have basically almost everybody a local performer,” he said.

All of the concerts begin at 3 p.m. at the Coral Gables Museum (285 Aragon Ave., Coral Gables), except for the finale June 16, which will take place at UM’s Gusman Hall. Here’s a full list:

Sunday: Amernet String Quartet. Music by Mozart, Dohnanyi and Tchaikovsky; with Yael Kleinman Hyken and Aaron Merrit.

Saturday, May 18: Delray String Quartet. Music by Mozart, Hoffmeister and Franck; with pianist Tao Lin.

Saturday, May 25: Children’s concert, with the Sona String Quartet. Music by Piazzolla and others.

Sunday, May 26: Amernet String Quartet. Music by Mozart, Tchaikovsky and Wolf; with pianist Paul Posnak.

Saturday, June 1: Sona String Quartet. Music by Mozart, Britten and Brahms; with pianist Marina Radiushina.

Saturday, June 8: Children’s concert, with the Miami Music Project Brass Quintet.

Sunday, June 9: Bergonzi String Quartet. Music by Mozart and Sibelius; with clarinetist Margaret Donaghue Flavin.

Sunday, June 16: Festival Finale. Music by Mozart, Janacek, Schnittke, Pärt, Falla and Piazzolla; with musicologist Frank Cooper, violinist Eli Matthews, cellist Joshua Roman and pianist Marina Radiushina.

Tickets are $20 per concert, or $100 for the series. Call 786-422-5221 or visit www.mainlymozart.com.