Fidelio is Beethoven’s only opera, so you’d think it would get performed more. But it doesn’t. The last time the National Symphony did it was 1970, though its rousing overtures periodically make it into Beethoven potpurri programs. So it’s a rare treat to see the whole thing at the Kennedy Center, if not fully staged, at least fully played by the NSO, joined by the Choral Arts Society and a bevy of talented soloists.

In terms of action, NSO’s Fidelio is a step up from last week’s pure concert version of Bluebeard’s Castle, though nothing as elaborate as the recently-concluded Così fan tutte. There’s no set, minimal props, but the singers do move around and make a perfunctory effort to act. Instead of costumes, they’re dressed entirely in black, which doesn’t help them stand out at all from the tuxedo-clad orchestra with whom they have to share a cramped stage. There were moments at Thursday’s performance when it seemed the NSO wasn’t willing to cede them any musical space either. After a rushed overture, the orchestra boomed over Jegyung Yang and Paul Appleby’s opening duet before director Christoph Eschenbach took the volume down to a more suitable background level.

Beethoven fans will recognize familiar tropes: noble heroes and wicked tyrants, thinly-veiled allusions to Napoleon and the composer’s own issues with authority—-although musically, the opera owes much to Mozart. The first thing you should know about the story is it’s named after a character that does not exist. “Fidelio” is the male alter ego of Leonore, a woman who is posing as a prison guard in order to locate and rescue her wrongfully jailed husband, Florestan. Leonore does such a good job at both prison work and looking butch that jailer Rocco wants to marry off his daughter, Marzelline, to her; somehow neither Rocco nor Marzelline find it odd that her husband-to-be is a soprano. Meanwhile, Florestan is in the clink because he did something to piss off Governor Pizarro, who wants him dead before a visiting government minister can discover that he’s jailing innocent people. He tasks Rocco and Leonore/Fidelio with the execution, but they refuse. When Pizarro returns, enraged and wielding a dagger, Leonore reveals herself to be Florestan’s wife and pulls a gun on Pizarro. Thus we learn that liberty always triumphs over tyranny, as long as liberty has a gun and tyranny has a knife.

The cast of Fidelio is strong all around, but not without soft spots. Melanie Diener is wonderful as Leonore, handling some demanding duets with skill and grace, including one with tenor Simon O’Neill at the end that contains particularly tricky runs. O’Neill (Florestan) leaves your ears ringing with an impassioned and, mostly, loud aria opening Act II. Eric Halfvarson, as Rocco, has some weird thing going on where he sounds like he’s about to sneeze for a good part of Act I. He eventually settles into a less apprehensive, dramatic timbre that’s nevertheless better suited to the Wagner roles he normally does. The Choral Arts Society, doubling as both chorus and prison population, is generally excellent. Jeffrey Gwaltney is quite good in a minor role of Prisoner #1, as is Kyle Ketelsen as the government minister.

The NSO galloped through the opera’s overtures with an energy that was mostly terrific. Mostly, that is, except…OK. It’s no secret the horns are not the NSO’s strongest section. Or second, or third strongest. But on Thursday, they were downright awful. Off key, badly timed, bleating like goats over the rest of the orchestra, it got so that you would cringe in anticipation of any fanfare. One of Eschenbach’s mandates is to improve the orchestra’s level of musicianship. No one expects miracles, but getting the brass to sound halfway decent would be a start.

The NSO performs Fidelio again on Saturday, March 17 at 8:00 pm at the Kennedy Center, 2700 F St. NW. $20 – $85. (800) 444-1324. In German with English surtitles.

Photos, clockwise from top left: Melanie Diener by Susie Knoll, Simon O’Neill by Lisa Kohler, Choral Arts Society by Margot Schulman, Eric Halfvarson by Lisa Kohler