The Boston Symphony’s feature on Thursday night was a rare treat, as unusual an item as could be found on any major symphony orchestra program anywhere—a concert performance of Karol Symanowski’s opera King Roger, Op. 46, in three acts lasting about 80 minutes and sung in Polish. Charles Dutoit, who regards this work as a specialty, conducted a cast of seven, with the Tanglewood Festival Chorus and the children’s choir of Voices Boston, and an orchestra that filled the limits of the stage. There were a lot of empty seats in Symphony Hall, perhaps 20%, but that only seems to indicate that both Szymanowski and the work that is considered his magnum opus were avoidably unfamiliar to many. But the performance was as exciting as it was precise.

Szymanowski (1882-1937) is hardly a household name even among musicians, but the history books regard him rightly as the most important Polish composer after Chopin. Whereas Chopin was an aesthetic descendant of the Austro-German and French traditions, and spent the major portion of his career in France, Szymanowski, born the same year as Stravinsky, lived most of his life in a strife-torn nation, inherited French Impressionism and Russian mysticism, and seasoned his art with a considerable proportion of Asian spirituality. King Roger seems to synthesize a big variety of post-Wagnerian and modernist and nationalist aspirations. Thus it’s not surprising to find Act I situated in a Byzantine cathedral, Act II permeated with oriental vocalises with dance rhythms and tambourines, and Act III in the ruins of a Greek temple—the whole opera taking place in 12^th-century Norman Sicily, which serves as an East-West crossroads. The leading role of the mystical Shepherd (Pasterz in Polish) combines a Hindu asceticism like Nilakantha’s in Lakmé with the visions of John the Baptist in Salome, while the role of Roxana reminds one of both Lakmé and Stravinsky’s Nightingale, and even a percentage of Brünnhilde in ecstasy in Götterdämmerung. But there is no death in King Roger, which is an opera about spiritual fulfillment through transcendence; instead of the glow of Grail at the end of the opera, there is the radiance of the rising sun, rather like the final climax in Schoenberg’s Gurrelieder (both King Roger and Gurrelieder end on an overwhelming C major).

The mysterious music of King Roger evades easy description. Lord Harewood, in Kobbé’s Opera Book, came close: “The music has something of the opulence and texture of Szymanowski’s contemporaries Strauss and Scriabin, with occasionally the sharp insight of Debussy.” The Strauss comparison applies to the complex orchestral texture, with what often seems like excessive internal counterpoint; it also suggests the way the musical substance follows the changes in dialogue at every point. Scriabin’s harmony, which often relies on a dominant-ninth sound with one extra note, is an obvious influence on Szymanowski’s—but the Stravinsky of The Nightingale and Firebird had this too, and Szymanowski’s harmony is often more cluttered with chromatic tones. The orchestration is large (quadruple woodwinds, seven trumpets, etc.) and often brilliant, seemingly influenced by Ravel and Rimsky-Korsakov, and yet I often felt the lack of a full string-ensemble sound; the violins were most often playing above the treble staff, and the cellos and basses most often in the lowest register, like big organ pedals (though the organ was there too, in the full triadic resonance of the opening cathedral scene, massive and splendid). If there is a structural deficiency in King Roger, it resides in the relative absence of clearly-defined sections, of perceptible motivic organization, and of a strong, recurrent tonal scheme (though C major does frame Act I and the opera as a whole).

But there is a good deal of harmonic framework that remains haunting in this opera, and one hopes that further hearing will reinforce the sense of what makes King Roger musically successful as something more than a big dramatic cantata—which is what it really is. I didn’t feel that the lack of staging was a hindrance to understanding the work, which in any case, judging from indications in the score, requires relatively little stage action.

A team of fine soloists, several of them appearing in BSO debuts, sang the central roles in King Roger: Marius Kwiecien (Roger II, King of Sicily), Olga Pasichnyk (Queen Roxana), Yvonne Naef (Deaconess), Edgaras Montvidas (the Shepherd), Rafał Maijzner (Edrisi, an Arabian wise man), Raymond Aceto (the Archbishop) and Alex Richardson (tenor solo). I especially want to point to the beautiful English horn playing of Robert Sheena, who had plenty to do and did it very well.

Mariusz Kwiecien was a mighty baritone, conveying all the regal pomp when needed, and the right degree of Angst the rest of the time. The Shepherd, on the other hand, is supposed to be bright and otherworldly, perhaps almost feminine, and Edgaras Montvidas brought a rich high-register expression to his interpretation. The part of Edrisi was sung by Rafał Majzner, but you’d think that such a counsellor’s role was more appropriate for a bass than a tenor, and Majzner sounded appropriately wise. (I was interested to read that he has a Ph.D., with a dissertation on the problems of singing Szymanowski’s operatic roles.) Olga Pasichnyk’s sound was lovely, especially in her wordless aria, if one can call it that, in Act II; the high A-flat that this song began on was recapitulated near the end of Act III.

The Tanglewood Festival Chorus had a fine strong sound, especially in the ecclesiastical segments of Act I (despite the role of an angry mob demanding the death of the Shepherd), and the clear enunciation made it plain that they had learned to cope well with the Polish language. The children of Voices Boston had an especially pellucid and appealing tone, which I remember from their performance in the Weinberg symphony that I reported on a while ago. The end of Act I has them singing “Amen” in a close-position E-flat major triad over a widely-spaced C-G open fifth in the orchestra, a sonority I won’t soon forget.

Charles Dutoit conducted with big and often subdivided gestures that seemed very precise. He obviously loves the music but he never went overboard in his admiration; he conducted what was needed. As an admirer of his Stravinsky recordings, I can enthusiastically approve.

The program booklet can be singled out for its ample supply of helpful notes and commentary by several different writers. The section “To Read and to Hear More…” mentioned several recordings, but not the one I studied from (Koch International-Schwann CD 314 014 K2), a Warsaw group conducted by Robert Satanowski, which I would say is fair, but nowhere near as good as last night’s live performance. As for last night’s English supertitles, they seemed like a good equivalent of the German text in the score (I do not read Polish), but they had too many misspellings that ought to be corrected before the next performances.

Mark DeVoto, musicologist and composer, is an expert in Alban Berg, also Ravel and Debussy. A graduate of Harvard College (1961) and Princeton (PhD, 1967), he has published extensively on these composers and many music subjects, most notably,  harmony.