Even in light of the relatively late replacement of violinist Sarah Chang (in what was termed a "program dispute"), it felt a tad incongruous to inaugurate the new season of the Schubert Club's august International Artist Series, which has played host to so many of music's greats, with the Naughton twins, Christina and Michelle: a young piano duo, Wisconsin-born and -bred, that few listeners had heard of.

But Tuesday's Ordway Center audience was anything but dissatisfied. The Naughtons may hail from just down the road, but they're easily the equal of the Labèques, the Pekinels (who, uniquely, sit back-to-back, eschewing eye contact) and the Twin Cities' own Hamanns, to name just three of the superlative sister teams that seem to dominate this sport. And the Naughtons' gem-studded program was calculated to remind skeptics that the four-hand medium--which, in this country at least, has never completely shaken off its variety-show associations--can claim its share of masterworks.

Like their colleagues, the Naughtons play as both a piano duet (four hands at one piano) and a piano duo (two pianos). The latter configuration, which offers grander sonorities and distributes musical substance more or less equally between the players while excluding competition for keyboard and bench space, boasts a more varied repertoire and, arguably, a higher standing in the musical hierarchy.

Tuesday's program moved naturally from one piano to two, beginning with Mendelssohn's 1841 "Andante and Allegro brilliant," dashed off for its composer to play with the formidable Clara Schumann, and concluding with Witold Lutoslawski's "Variations on a Theme by Paganini," written a century later for performance by the impecunious café duo of Lutoslawski and fellow Polish composer Andrzej Panufnik. (It must have been quite a café!) Along the way came Schubert's restive "Lebensstürme" (Life's Storms), Brahms' "Variations on a Theme by Haydn" (heard last month in its orchestral garb in the same hall), Ravel's dark "La Valse" and Mozart's sunlit D-major Sonata, K.448 (a favorite of those who tout the so-called "Mozart effect").

The Naughtons' playing could hardly have been better. The often-impetuous "Haydn" Variations had the flexible pulse Brahms needs; Ravel's frenzied climax was precisely calibrated. The Mozart, given just the right weight, was exceptionally convivial and conversational. And after so much beautiful piano tone, it was almost a relief, in the Lutoslawski, to hear the sisters make an ugly sound.