DUBLIN - Theaters are closed here on Sunday - the Abbey, the Peacock, others are all dark - but hark! there are lights on at the entrance to the Gate Theatre. Ask what's happening, and you will be told that the cast of Brian Friel' new play, "Performances," is giving a concert. Excuse me? Intrigued by that puzzle, you go in and discover the Alba String Quartet holding sway in the theater, with a brief but excellent program of Schubert's Quartettsatz in C minor, Mozart's Quartet in E flat, Webern's "Langsamer Satz," and Janacek's String Quartet No. 2. This last item on the program, Janacek's 1928 "Intimate Letters" quartet, provides for yet another "first," unless you have already attended a chamber-music concert that had been rehearsed nightly, with audience, for over a month. This is how all those strange items come together: Friel's play is about Janacek and his decade-long pursuit of Kamilla Stosslova, a happily married 26-year-old when the composer, age 62, became possessed with her. "Consummation" of the one-sided affair came in Quartet No. 2, an ecstatically happy, "Tristan"-passionate, achingly beautiful work by Janacek at 74, at the end of a troubled, but ultimately redeemed, life. The play - by the author of "Translations" and "Dancing at Lughnasa" - has a fictional graduate student researching Janacek's life, it brings in the already dead composer to answer her questions, and completes the cast with members of the Alba: Nicola Sweeney and Jana Ludvickova (violins), Fay Sweet (viola), and Tony Woollard (cello). The musicians perform the first two movements of "Intimate Letters" off-stage, while the text of some of those letters is spoken and discussed on-stage; then the quartet plays on-stage and talks about the music while the actor playing Janacek (Ion Caramitru), contemplates some of letters, projected on the walls, in silence. On Sunday then, the Alba Quartet musicians stepped out of their "roles" as the quartet in the play, and after playing what Richard Pine's program notes call this "massive soliloquy on longing and passion," more or less as background music for a month - and performed it, front and center, in its entirety, uninterrupted. How was it? Glorious. The Alba is a young group, with a young, vigorous, somewhat raw sound, quite different from the end-of-life, Verdi "Falstaff"/Shakespeare "Tempest"-category "Intimate Letters" may be thought to require. And yet, the technically flawless, deeply-felt reading came across superbly. There are so many complexities and contradictions about this work, not least of it being in the music itself: Janacek had nothing but disdain for Wagnerian romanticism and "pompous chord progressions," but his two quartets are quintessentially romantic. The Alba managed to resolve paradoxes all evening long: those of excess and classicism in the Schubert, elegance and deep feelings in the Mozart, chromaticism and gentle, "old-fashioned" tonality in the Webern, and - especially - bridging pain and happiness in Janacek's music the way the composer managed to accomplish that both in music and life. "Intimate Letters" says one is never too old for passion; the Alba performance proved one is never too young to have mature wisdom of expression. Janos Gereben/SF (In Wexford, 10/20-22, in London, 10/23-27) www.sfcv.org