Southern Arizona Symphony Orchestra Conductor Linus Lerner waited until Sunday's final concert of the 2014-15 season to present was was arguably the semi-professional orchestra's most challenging program.

The concert opened with Mussorgsky's moody "Night on Bald Mountain" and closed with Elgar's demanding "Enigma" Variations.

"It's a very hard piece to play," Lerner said in introducing the work in the concert's second half. "I would say it's an achievement for us. We can play anything now."

"Enigma" has a few unsavory nicknames among musicians. It's devilishly difficult with 14 variations all melting into one. Playing it is almost like peeling an onion, each new layer exposing a more pungent and gorgeous aspect of the whole. It opens with a familiar slow passage. You know you've heard it before — possibly as the backdrop to a commercial on TV, maybe as a the soundtrack of a TV show — but you can't quite place it. Variation two takes the theme in a slightly faster tempo and then every variation that follows builds on it.

Lerner had warned the audience that they would lose track of the variations after a spell, and by the sixth or seventh, I was a bit lost. But I found my place when the orchestra played the gorgeous "Nimrod" ninth variation — the piece that was the theme for the London Olympics in 2012. Lerner guided the orchestra in what was the most sublime four minutes of the afternoon. SASO performed it gorgeously. The strings soared and swayed with striking precision and the brass finale, with the rumble of percussion in the backdrop, put an exclamation on the performance.  It was as close to perfect as you can get without popping in a CD of the London Symphony Orchestra.

Hperbole? Perhaps, but the standing ovation Sunday's audience paid SASO and Lerner would support it.

The concert opened with Dallas violinist Chloé Trevor joining the orchestra for Max Bruch's Violin Concerto in D minor. Wow, where in the world did SASO find her? Trevor was wonderful. The sound she coaxed from her 18th century instrument, borrowed from her violin-playing mother who was in the audience Sunday, was warm and bright.

Bruch's solo passages are demanding. The player dances over lightening fast chord progressions that scale the fret. It's a heavy load that Trevor, dressed in a bright blue gown, her auburn hair flowing down to the middle of her bare back, performed with the confidence of someone who has this music committed to muscle memory.

In the rare moments when she was not playing — there were only a few and they didn't last long — Trevor swayed slightly to the beat being performed admirably by the orchestra, her movements matching those of Lerner, whose conducting style is infectiously energetic and boundlessly impassioned. (Good news; His new podium has a railing to prevent him from toppling off the platform when he gets a little too energetic.)

If you were watching closely, you could see Lerner almost singing along to the score, summoning the brass section to create an eerie wail. He turned to the strings then the woodwinds and on his cue they joined in to create a lush melody that became a stirling soundscape filling St. Andrew's Presbyterian Church Sunday afternoon. 

The Elgar Variations was one of the biggest challenge the orchestra has faced under Lerner — or any SASO conductor, really — but it certainly will not be the last. Lerner has programed Berlioz's Symphonie fantastique, a work that has a reputation for being an epic event for major orchestras, as next season's finale early next May.