Outdoor orchestral performances are a long-standing summer tradition: a way to present classical music to a wider public — including picnickers on blankets on the lawn — in more laid-back surroundings than a traditional concert hall. The question is whether such concerts are still as beloved as tradition would have us believe. The National Symphony Orchestra opened its NSO@Wolf Trap series Thursday night to row upon row of empty seats.

Who, really, is it playing for? Summer concerts like this one — the requisite all-Tchaikov­sky program, balancing the Violin Concerto with a group of ­ballet excerpts, and topping it off with the “1812 Overture” (but no fireworks) — try to walk the line between pandering to a mass audience and offering tidbits for a discriminating one, but offer too little to each group to hold the interest of either.

If you want to win over casual attendees, then keep the tone that Emil de Cou, the NSO’s former associate conductor and the current conductor of the NSO@Wolf Trap series, struck when he took the stage at the start of the evening, in blue jeans, and offered a funny-hokey intro to the season, getting the biggest crowd reaction when he announced the video-game music event the following night.

If you want to win over music lovers, then play up the debuts of Caroline Goulding, the 18-year-old violin prodigy who soloed in the concerto, and Pietari Inkinen, the 31-year-old Finnish conductor who led the orchestra with an air of bemused insouciance, appearing slightly nettled by the audience’s persistent clapping in what, during the regular season, would be accounted the wrong places, and sporting a white garment that looked like a cross between a trench coat and a lab coat and which gave him the air of an impassioned pharmacist.

But trying to please everyone resulted in a concert that was as tepid as its attendance indicated. Part of the issue was the laid-back approach of the two debutants. Inkinen sports a jaunty, easy carelessness that yields music attractively smooth but sorely in need of several jolts of caffeine. In the “Nutcracker Suite,” he seemed to give up and just go through the motions of providing the audience with the nuggets of sugar it wanted.

Goulding is a skilled violinist well on her way to an important career (she recently won an Avery Fisher Career Grant and was nominated for a Grammy for her debut album on Teldec), and she got a throaty warmth from her Stradivarius rather than simply yielding to the temptation of making pretty singing sounds. Yet there was still something slightly obedient about her reading of this concerto: It was beautifully executed but not yet fully authoritative. Both young artists may have been trying to play down the traditional showiness of the work, but they toned down too far; the second movement was pallid, and it took them a while to get on the same page at the start of the third.

The NSO fielded a team with plenty of backup players, as tends to be the rule in summer concerts of this ilk. The violins sounded oddly anemic, though the cellos and violas offered a nice tangy bite in the “1812 Overture”; and the brass sounded over-heavy from the outset (two dances from the opera “Eugene Onegin”), as if Inkinen hadn’t fully worked out the balances. Most bewildering was the moment toward the end of the “1812 Overture” when, after the first assault of slightly dutiful-sounding cannon fire has helped build up a ferocious head of steam, the orchestra is all caught up in a downward-spiraling frenzy that, here, sounded as if all that energy was running out a bathtub drain. Inkinen did get it whipped up again into an appropriately chaotic finish, at least enough to give some audience members a sense of having experienced an Event before heading for the exits.

NSO@Wolf Trap

Highlights include “Sweeney Todd,” July 22; the 5 Browns, July 28; Tan Dun’s “Martial Arts Trilogy,” Aug. 5; and Arlo Guthrie and Time for Three, Aug. 6.