LENOX -- After the years of suspense, after the concussion and cancellation, after the hurrahs, hype and handshakes, Andris Nelsons arrived at Tanglewood looking like not just a music director but an anointed champion.

In an all-Dvorak program Friday night and a gala Saturday night, the Boston Symphony Orchestra's director-elect showed why the BSO had grabbed him. His command of the orchestra was sure; his ideas about the music were sometimes unorthodox but the more convincing, even beguiling, for the fresh light they shone.

Expectation and excitement ran high in the large audience Friday when the Latvian conductor first stepped onto the stage of the Shed. Though youthful at 35, he moved a bit heavily.

When he briskly mounted the podium and went to work, though, an unmistakable force rushed from the stage. With his large repertoire of energetic gestures - everything from a pinkie twinkle to a lunge or swoop - he often looked like a possessed magician waving his wand.

Magicians conjure out of the air, which is also what conductors do. The BSO followed Nelsons through every twist and turn, every hush and rattle, every heaven-storming climax. The sound was rounded and opulent yet retained transparency to let inner parts through. The ending of Dvorak's Eighth Symphony on Friday and Ravel's "Bolero" on Saturday went through the roof.

After an opening weekend when three conductors couldn't rouse the orchestra out of a general lethargy, it was as if a cleansing storm had blown through.

The gala was not quite the success it should have been. The idea of splitting the program between the student Tanglewood Music Center Orchestra and the senior orchestra, all under the new director, fitted the occasion, and the young musicians played their hearts out for him in the suite and Presentation of the Rose from Strauss' opera "Rosenkavalier."

The student group lacked ingrained ease with the repertoire, though. And while Sophie Bevan, Angela Denoke and Isabel Leonard sang ardently as Sophie, the Marschallin and Octavian, the presentation scene looked and sounded stilted with the singers directing their raptures to the audience. Leonard's mezzo soared luminously above the others. Tanglewood, again, kept the house lights low, making it difficult for the audience to follow the printed text, and therefore the action.

Appointed in 2013, Nelsons officially takes charge this fall. He had been at Tanglewood only once before, in a 2012 Stravinsky-Brahms program. He missed a return last summer because of a concussion that kept him at home in Germany, but his experience with the BSO was obvious in their rapport. Fine weather and a large audience greeted him both nights.

For the BSO's half of the gala, Nelsons wrung a deep, Tchaikovsky-like melancholy from Rachmaninoff's "Symphonic Dances," his last composition. At times sinister, at times voluptuous, the performance punched the work's message of fate home with the climactic "Dies irae" death chant. As the closer, "Bolero" proceeded on its relentless, hypnotic course to the shocker ending.

The Dvorak program began with "The Noonday Witch," a folk tale set to creepy music, played by the BSO for the first time, and climaxed in his outdoorsy Eighth Symphony. Tempos were in almost constant flux, and emphases were not always in their accustomed place. Rather than arbitrary, the effects seemed a natural enhancement of Dvorak's landscape.

As star soloist, Anne-Sophie Mutter offered up a garish rendition of the Dvorak Violin Concerto. The razzle-dazzle factor was high, perhaps to lend a narrative line to a somewhat rambling concerto. Nelsons had the orchestra supporting or challenging her every step of the turbo-charged way.

Questions may arise later about Nelsons' free and easy ways with tempo, but for two nights, Dvorak, Rachmaninoff and Ravel sounded terrific in the orchestral plumage in which he arrayed them. He'll be back this weekend with violinist Joshua Bell as soloist and a couple of contemporary works in tow.