Now in its third season, the Black Pearl Chamber Orchestra is finding itself a niche doing typically classical things with less-than-typical participants. Oriented toward African American musicians, founder/music director Jeri Lynne Johnson is creating audiences that seem new to Haydn and Mozart - and doing so with concerts that are first-class on every level.

Though some listeners Saturday at the packed Philadelphia Episcopal Cathedral could be heard quietly humming along with Mozart's beloved Sinfonia Concertante for violin, viola, and orchestra, others applauded between movements - showing not just appreciation, but that lots of listeners were new to classical concerts.

The program began with a seldom-heard piece by the so-called Black Mozart, Joseph Boulogne, Chevalier de Saint Georges (1745-1799), who was born in Guadeloupe but educated in Paris, eventually becoming a composer and such a fixture among Paris aristocracy that he was imprisoned during the French Revolution. He was represented by his Symphony No. 2 (Op. 11, No. 2), written during an era of fairly strict musical conformity (fun, frothy, elegant - or else!), though one can hear that he injected his own unexpected breaks with the usual melodic symmetry and rhythmic regularity, before reeling himself in to satisfy the tastes of the times.

Elsewhere, the program had a hidden undercurrent - French horn writing that anchors Haydn's Symphony No. 44 ("Trauer") and Mozart's Sinfonia - that was especially apparent thanks to the solidity of Larry Williams and Katy Ambrose. Haydn's adagio movement shows the composer writing something of a melody without end - and one you don't want to end - that conductor Johnson paced with particularly poetic skill. She chose not to use harpsichord (lately the fashion with Haydn symphonies), though the solidity of the performance combined with the cathedral's generous acoustics assured that the piece had all the sound it needed.

The concert's overall atmosphere felt both relaxed and celebratory. Listeners brought well-behaved children. Johnson mingled in the crowd at intermission. The Mozart soloists, violinist Kelly Hall-Tompkins and violist Robin Fay Massie, had obviously worked out their interpretation in great detail. In a piece where violin and viola often complete each other's musical sentences, these two had a sense of witty banter that made their performance anything but another encounter with Mozart's masterpiece.