The Michelangelo String Quartet. (Marco Borggreve)

The 90th-anniversary season of free concerts at the Library of Congress introduced a new ensemble to the Washington area on Saturday afternoon. The Michelangelo String Quartet, formed in 2002, had somehow eluded my notice up to this point. With its relatively new second violinist, Daniel Austrich, who replaced founding member Stephan Picard in 2012, the group’s weaknesses temper enthusiasm for its strengths.

Beethoven appears to be one of the quartet’s specialties, as it has performed the complete cycle of the composer’s string quartets and recorded some of them. The F major “Razumovsky” Quartet (Op. 59, No. 1) was the highlight of this concert, as the group negotiated the music’s complexity and breadth with skill. A reduced and balanced tone from all four players produced a playful second movement, while the third movement had the patience and intensity that were missing in some of the other pieces on the program, as Beethoven peeled apart the layers of his music’s themes to inspect them from all sides.

First violinist Mihaela Martin tended to dominate far too often, with a knife-edged sound and some perilous intonation at the high end of the E string, in the minuet of Haydn’s Op. 77, No. 1 Quartet, for example. The Haydn, in general, was unsettled where it should have been genial, humorless when it should have had its eyebrows raised. The group captured much of the grim humor of Shostakovich’s Third Quartet (Op. 73), especially in its acidic interpretation of the third movement. In the spots where the first violin dropped out, the reticence of the other three players was spotlighted, and the intense slow movements that conclude the work were more snoozy than stark.

Downey is a freelance writer.