Leonard Slatkin vividly recalls the nightmare of conducting a major symphony orchestra for the first time: "I simply moved my arms and kept my mouth shut, hoping that would be enough to carry me through." In his case it was, but the scars remain. And nothing has changed. Few novice conductors survive this cruel rite of passage, and for most the opportunity even to rehearse a professional orchestra simply never arises. Years of study and immense talent are no substitute for experience, and there is always a pool of experienced conductors--usually from other countries--to fill the void. Hence the dearth of American conductors.

The National Conducting Institute--which Slatkin founded and directs--recently selected four conductors whose only experience is with amateur orchestras and drilled them for three weeks in the myriad aspects of orchestral leadership. The program includes five working sessions with Slatkin, five rehearsals conducting the National Symphony Orchestra, and Saturday night's performance with the NSO in the Kennedy Center Concert Hall. As Slatkin points out, the real moment of truth is not the performance itself, but the rehearsals, where a hundred professional musicians await transformation into a single, immaculately balanced instrument. A conductor who lacks absolute authority or who wastes time with windy explanations has nothing to offer in performance but a slug of notes.

The rehearsal Saturday morning was illuminating. Slatkin grabs a conductor's arm and demonstrates with a dip of the wrist how to cue one section of the orchestra within a gesture that phrases for another section. Slatkin tells another conductor, "You're going to be out of time. Make your point and go on." He advises yet another where to begin a tricky passage and interrupts the conductor's tentative remarks: "Just sing it." He teaches protocol: how to walk to the podium; how to bow; how and when to include the orchestra in response to applause. He calls these seemingly simple maneuvers "the look"; he has it, they do not.

They watch as he rehearses his own brief part of the program. He is very specific, and he gets what he wants immediately: stretch the triplet, keep that color, phrase in three groups of two. A few spare, expressive motions convey it all. It looks easy.

Against all odds, Saturday night's free concert was excellent. Not a single conductor was tentative, and all delivered performances of individual profile and character. Jason Weinberger's Wagner ("Tannhauser" Overture) flowed majestically; Harry Davidson's Mendelssohn (Symphony No. 4) was acutely detailed and powerful; Alexander Mickelthwate's Copland ("Appalachian Spring" Suite) was refreshingly tender and lyrical; and Ki-Sun Sung delivered a crackling, rhythmically secure interpretation of Stravinsky's "Firebird" Suite. The luminous clarity and misted fragrance of Slatkin's Debussy--"Prelude to the Afternoon of a Faun"--arose from tight orchestral balance and long-lined, supple phrasing.