This summer the Wolf Trap Opera will perform Florian Leopold Gassmann’s “L'Opera Seria.” (Carol Pratt)

Summer opera. Imagine, if you will, lazy picnics on the lawn, fireflies in the air and the gentle strains of an aria by — Florian Leopold Gassmann.

Who? Come to Wolf Trap and find out.

In the classical world, the term “summer season” often evokes pops concerts and musicals — but “summer festival” evokes the intriguing and offbeat. The Wolf Trap Opera is generally far more the latter — not least because its singers are mainly unknown and its programming is tailored to the strengths of its cast in any given summer.

The Wolf Trap Opera first picks the singers it wants, then finds an opera that will fit them. This is the advantage of being a training program more focused on artists than on selling tickets. The seats in the diminutive Wolf Trap Barns are usually full whatever the repertoire, because with only a few hundred places — along with the liberal policy of allowing people to bring their drinks in with them — it’s easy to fill the house. And choosing the artists first means the company avoids the common pitfall of trying to find singers to shoehorn into roles that don’t quite fit.

At this point, Wolf Trap has an impressive track record: a startling number of successful American singers today have passed through its program. (There were no fewer than 13 Wolf Trap alumni in the Washington National Opera’s recent “Ring” cycle, including Christine Goerke and Alan Held; Held, this year’s Wolf Trap artist-in-residence, will hold a public master class on June 27.) Its measure of success is how well it does by its singers; audiences are, as it were, along for the ride.

(Aurélia Fronty/For The Washington Post)

A sad note this summer is the loss of the Castleton Festival, another training ground for young professionals, founded by the late Lorin Maazel but on hiatus and struggling with its future now that he is no longer leading it. That festival began in 2009 with the operas of Benjamin Britten, and Wolf Trap this summer leaps into the breach with “The Rape of Lucretia” (June 10-18), an exquisite chamber opera originally written for Kathleen Ferrier. (Its American premiere was on Broadway and starred Kitty Carlisle.) Wolf Trap’s Lucretia is J’Nai Bridges, a “young professional” with an impressive résumé and a host of awards (including the Marian Anderson award in 2012). If you miss her this summer, you can hear her next year in Beethoven’s Ninth Symphony, Christoph Eschenbach’s final performances as music director of the National Symphony Orchestra.

Not all of Wolf Trap’s offerings are offbeat. In recent years, the company has revived the practice of doing one show a summer at the Filene Center, with the National Symphony Orchestra; this summer, it’s “La bohème,” conducted by Grant Gershon and directed by Paul Curran. (Aug. 5.)

But if you’ve never heard of Gassmann, you’re not alone. An 18th-century composer active in Venice and then in Vienna, he wrote “L’Opera Seria” in 1769, and its Wolf Trap performances (July 15-23) will be the first ever given in America. The subject, though, is topical enough: backstage drama during the production of an opera, at the end of which the presenter absconds with all the money. How better to prepare young singers for their professional careers?

Other summer highlights:

If the future of classical music is on your mind, the National Orchestral Institute is another reason for optimism. This program selects gifted young players from across the country and brings them to the University of Maryland for a month of intensive lessons, rehearsals, master classes and performances of all stripes, including three marquee appearances by the National Festival Orchestra, made up of all the participating students. This year’s conductors include James Ross (whose leadership at U-Md. has helped spark some of the most interesting orchestral programs I’ve ever seen, such as the choreographed collaborations of “Appalachian Spring” and “Afternoon of a faun”), who leads an evening of American symphonies June 11, and Osmo Vänskä, the acclaimed conductor of the Minnesota Orchestra, on June 25.

Minnesota Orchestra conductor, Osmo Vänskä. (Kaapo Kamu)

“Firebird” Creator Janni Younge with puppets. (Courtesy of Wolf Trap)

A pinnacle of Wolf Trap’s summer is a new “Firebird,” co-commissioned with several other groups from a member of South Africa’s Handspring Puppet Company — the team responsible for “War Horse.” The National Symphony Orchestra under Cristian Macelaru will play Stravinsky’s score to live puppet accompaniment in what is being billed as a spectacular and colorful performance (July 23). Also of interest on the NSO’s Wolf Trap calendar are a performance by the star pianist Yuja Wang, playing Ravel under Lionel Bringuier (July 8), as well as one by Chad Hoopes, a violinist who will play the Tchaikovsky concerto with Stéphane Denève (July 29).

Two small and ambitious opera companies bring their own summer theater. The InSeries is tackling Beethoven’s “Fidelio” on a small scale (June 18-26), transporting the action to a South American dictatorship. And the nascent Vermont Opera Project is bringing its inaugural production, Ricky Ian Gordon’s “Orpheus and Euridice,” to the National Gallery (Sept. 10-11).

Finally, the Washington Concert Opera will host a festive concert in celebration of its 30th anniversary (Sept. 18), starring Vivica Genaux, Angela Meade, Michele Angelini and Antony Walker, the group’s music director, as conductor — bringing us into a busy fall season ahead.