If you surf YouTube for Tessa Lark videos, there she is performing Bartok, Mozart and Bach. There she is fiddling on some bluegrass tunes with a banjo player - in the same concert as the Bartok. There she is recording the Patsy Cline hit "Faded Love" with composer Mark O'Connor.

Will the real Tessa Lark please stand up? Well, she will this weekend at Musical Masterworks, when she performs O'Connor's aptly named "Appalachia Waltz" with cellist Edward Arron and double bassist Kurt Muroki and when she joins a quintet including violinist/violist Erin Keefe and pianist Pedja Muzijevic for one of the greatest hits of the chamber music repertoire, Schubert's "Trout" Quintet.

Lark was a surprise star in last season's Masterworks performances, and for the concerts Saturday and Sunday at the First Congregational Church, the 24-year-old Kentuckian will be part of a stellar lineup. Bosnian-born pianist Muzijevic has performed with orchestras worldwide, and violinist Keefe has just been appointed concertmaster of the fine Minnesota Orchestra. Keefe will be featured in Bartok's Roumanian Dances for Violin and Piano.

Because the O'Connor trio and the Bartok duo are drawn from music heard in the mountains (though different mountains on different continents), series music director Arron says, "The most pleasurable thread to pull this program together is that of folk music."

Schubert's "Trout" quintet drew its nickname from a movement with a set of variations on his song "The Trout," and it's unusual for its addition of a double bass to a piano quartet.

The concert will open with Rossini's operatic little String Sonata No. 3 in C Major, and it concludes with Schubert's high-energy melodic romp of a quintet.

All good …

- MILTON MOORE

Musical Masterworks,

5 p.m. Saturday and 3 p.m. Sunday, First Congregational Church, 2 Ferry Road, Old Lyme; $35, $5 for students; (860) 434-2252, musical-masterworks.org.