The Recital Hall of the University of North Carolina at Greensboro’s School of Music was nearly filled with music lovers, eagerly anticipating one of the glories of the chamber music repertoire, Mozart’s String Quintet No. 4 in G Minor, K.516. This week’s Greensboro Symphony Masterworks series guest artist was violist Roberto Díaz. His inspiring programming of imaginative works featured his instrument on both the orchestra and chamber music series.

Frank Bridge (1879-1941) is best known as composer Benjamin Britten’s most important teacher. As a conductor, Britten promoted many of Bridge’s works. As a violist, Bridge was a member of both the Joachim String Quartet and the English String Quartet. The latter gave the premiere of Debussy’s Quartet in Britain. As a composer, Bridge’s style is radically divided between readily approachable tonal works before World War I and more complex and modernist works afterward.

Roberto Díaz joined GSO principal violist Scott Rawls for a real rarity, Bridge’s “Lament” (1915). Rawls prefaced the performance with some background. The Frank Bridge Trust has attempted to publish all of the composer’s works, many of which only existed in manuscript. This poignant duo is the only surviving movement of three from a work inspired by the tragic sinking of the passenger liner Lusitania. The work is a real gem that deserves frequent performance. Its mood is similar to that of Fauré’s “Elegie” or Ravel’s “Pavane,” and the music is immediately attractive and interesting. Díaz’s baritone-like 1570 Amati made a fine contrast with the darker timbre of Rawls’ early 20th-century Italian viola. A mellow singing line is set against delicate pizzicatos for part of the score. Both players brought out the textural qualities of this gossamer score.

Many commentators have pointed out the importance of Mozart’s having twice conceived major pairs of works in C Major and G Minor. His Viola Quintet in C Major, K.515, was completed April 19, 1787, followed by the Viola Quintet in G Minor, K.516, on May 16. In the summer of 1788, he completed Symphony 40 in G Minor, K.550, on July 15, followed two weeks later by Symphony 41 in C Major, K.551. All represent the pinnacle of the composer’s achievement. The presence of two violas along with the use of the dark key of g minor in the Quintet No. 4 contributes to the score’s melancholy character. The heart of the work lies in the slow third movement and the continued dirge-like cavatina that opens the first half of the concluding allegro. Dmitry Sitkovetsky made an intriguing observation before taking the first chair violin for the performance. He drew parallels between Haydn’s Seven Last Words of Christ on the Cross, Op. 51, and “the dramatic pauses and questioning” in the third movement and cavatina of K.516.

Sitkovetsky was joined by assistant concertmistress Wendy Rawls, assistant principal cellist Philip von Maltzahn, Rawls, and Díaz. The balances among the instrumentalists was excellent, and their playing was stylish, with good intonation and effective phasing. The sheer joy of music-making — with knowing smiles exchanged between artists as the music was taken up by players in turn (as in a stylized soccer game) — is one of constant satisfactions of this fine series.

In response to the enthusiastic reception of the performance, the ensemble encored the fast allegro portion of the last movement with Sitkovetsky setting a challenging faster tempo that was matched by his colleagues. This was one of the classic rewards that comes from the spur-of-the-moment risk-taking of live performances.