Turnover among musicians in longstanding ensembles is inevitable. Some, like the Guarneri String Quartet, simply disband. The esteemed Tokyo String Quartet - founded at the Juilliard School in 1969 by four Japanese musicians who studied together in Tokyo - will soon have none of its original members. The violist, Kazuhide Isomura, a founding member, and the second violinist, Kikuei Ikeda, who joined in 1974, recently announced that they would retire from the quartet in June 2013.

The first violinist, Martin Beaver, and the cellist, Clive Greensmith, are auditioning new members to replace their colleagues. Among the ensemble's final projects in its current incarnation is a two-season series at the 92nd Street Y, where it has been in residence since 2003. It focused on Beethoven in recent concerts there, offering the complete string quartets paired with piano sonatas. Bartok is now in the spotlight, with each of his six quartets paired with one by Haydn, a pivotal figure in the development of the genre.

On Saturday evening, in the first concert of the new series, the program opened with Bartok's poignant String Quartet No. 1, which blends late Romantic harmonies with the terse rhythms and Hungarian folk melodies that would shape his ensuing works in the genre. The opening theme, described by the 27-year-old Bartok as his "funeral dirge," reflected his suffering over an unrequited love; it was conveyed with plaintive intensity here. The rest of the work unfolded in an equally vivid palette, with the musicians etching sharp contrasts between moments of introspection and those of rhythmic exuberance.

Haydn also evoked Hungarian folk music in works like his String Quartet in D (Op. 20, No. 4), which came next in the concert. The vibrant, energetic interpretation revealed myriad details throughout, particularly in the inventive Presto Scherzando, which ends in witty fashion.

As the Tokyo quartet nears the end of a major chapter in its history, it shows no sign of weariness. It played here with a commitment and a passion that rendered the third work, Schumann's String Quartet in A (Op. 41, No. 3), a treat.