“The magic word tonight is ‘Intermezzo,’ ” said Gianandrea Noseda, with the air of a “Sesame Street” host announcing that this episode was brought to you by the letter C — the same mixture, that is, of mild, clean humor and didactic clarity.

Some might have thought the magic words were “Renée Fleming,” looking exquisite as a china doll in her peach-lined black dress. Others might have cited “new work” — the program’s featured piece, Kevin Puts’s “The Brightness of Light,” in which Fleming took the role of the painter Georgia O’Keeffe opposite Rod Gilfry as photographer Alfred Stieglitz, her husband. But the overall theme of the National Symphony Orchestra’s program on Thursday night, according to Noseda, was the intermezzi, or in-between spaces: the pauses between acts of an opera, scenes of Puts’s multipart work or, Noseda said, the distance between forming thoughts in your head and writing words on the page — a telling metaphor for a critic.

Thursday night’s concert was my last as classical music critic of The Washington Post. I am stepping down to pursue other projects and to allow Washington’s music scene a fresh perspective from another critic. (The search for my successor is ongoing.) It was fitting to spend this last evening with the NSO, the orchestra I have reviewed for The Post more than any other ensemble. And it was fitting that the concert was about in-between spaces, since the NSO continues to occupy them. The orchestra is in between being very good and having trip-ups from brass and winds, and in between playing with engagement and simply producing notes as if merely counting out beats until the piece is over.

Intermezzo, in this sense, could also describe the arc the NSO has traversed over my 11 years in Washington, from the disaffected, sloppy ensemble that Leonard Slatkin left when he departed in 2008 to the group that’s starting to taste real international demand under Noseda. Those ­in-between years have seen ups and downs. There have been some memorable highs: Mahler’s second symphony under Iván Fischer; Christoph Eschenbach’s “Der Rosenkavalier” with its warmth and elan (and, again, Fleming); performances led by Herbert Blomstedt and Donald Runnicles; and Slatkin’s program juxtaposing Paganini’s violin concerto, with Hilary Hahn as soloist, and David Del Tredici’s “Final Alice,” with Hila Plitmann as vocal soloist — two awe-inspiring displays of virtuosity and one of my favorite orchestra concerts of my career. The lows were the mediocre evenings when the players didn’t really seem to care, such as those piercing but plodding wind passages or lackluster brass entrances that tarnished even last week’s “Tristan und Isolde” and, on Thursday night, the opening of Strauss’s “Also Sprach Zarathustra,” one of the most famous passages in the repertory.

Progress never happens in a straight line. The orchestra has moved forward in terms of ability, with lots of new players, a richer string sound and the capacity to create magical moments in Act II of “Tristan” at Lincoln Center last week. It has moved back a bit in terms of new music, which was a more vital and organic part of the season under Slatkin, though Lera Auerbach’s “Arctica” in April and Puts’s piece this week are big gestures toward innovation.

“The Brightness of Light” offers a kind of Ken Burns take on orchestral music. A huge screen covering the organ balcony over the stage projected images and text all the way through: O’Keeffe’s early paintings, love letters between her and Stieglitz, photographs of her as a young woman and of the couple together. The music took its narrative role seriously and literally, from the rapturous sunbursts of sound that opened the piece beneath images of radiant watercolors to the passage in which Ying Fu, the associate concertmaster, offered some raspy, scratchy violin playing to accompany O’Keeffe’s letter about her own attempts on that instrument.

The story itself raised a lot of questions. Stieglitz emerges as a bit of a jerk (he was married when he met O’Keeffe, and he cheated on her, as well), and having a male composer offer the male point of view (“A woman’s soul, laid bare in all its beauty!” Stieglitz crows, probably sincerely but with an unwittingly patronizing undertone that echoed many more recent #MeToo offenders) created an unexpected perspective on an artist who is seen as a feminist icon. The focus is supposed to be the music, which was ardent and capable, now animated by rapid heartbeats of percussion, now pulling away to a solo piano spinning out a Bach-like melody. But the music sometimes seemed merely a vehicle for delivering the story rather than a means of amplifying it. Gilfry sounded a little dry, appropriately cast for an older man, but the piece is a nice vehicle for Fleming, whose top is no longer as creamy as it once was but who filled the role of beautiful young woman very nicely on all counts.

For the two Strauss pieces that bookended the Puts work, the projection screen showed an image of the organ behind it — mirroring my frequent feeling, after living 11 years in Germany, that German music played in American concert halls often sounds like a facsimile. The evening opened with the second symphonic interlude from Strauss’s opera “Intermezzo,” called “Dreaming by the Fireside,” music as warm and caressing as licking flames. Please play well, I thought. I want our last outing to be wonderful.

But life doesn’t work like that, and relationships don’t work like that. In the drive to be perfect, whether you’re an orchestra or a writer, there are often sloppy moments, things you’d rather overlook, times your ambition outstrips your ability — times when the distance, or intermezzo, between the ideas you’ve framed in your mind and the way you present them to the public yawns so wide you despair of the meaning ever coming across.

People often say that an orchestra is a metaphor for excellence. But it’s also a metaphor for life itself: not an isolated event but an activity to be engaged in, through dry spells and misfires and, sometimes, moments that overwhelm you with their sheer magnificence. Orchestra lovers are like fans of a baseball team, who accept that it sometimes does badly and exult when it does well, and like a sportswriter, I call out the bad moments while, in my heart, always rooting for the group to do its best. In that spirit, I can say that “Zarathustra” on Thursday had some shockingly lackluster spots, like the dry, piercing flute notes on which the piece ended, and some richly beautiful ones that made me appreciate the depths of a score usually remembered only for its first 60 seconds.

Does that mean I don’t care about the NSO, or that you shouldn’t? No, it means that you should figure out for yourself what your relationship with this orchestra, and this music, holds for you, while watching its current ascent and hoping what we all hope for ourselves, as well: that it can continue to develop toward its very best.

The program repeats Saturday evening; Friday’s concert will feature a Mozart symphony in place of the Puts.

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