The Honolulu Symphony Orchestra season is turning out to be a mini-course in acoustics.

Audiences do not often spend time thinking about acoustics. It is generally an issue between musicians and architects, one that surfaces briefly at the opening of a new hall and then fades into the background.

Saturday's concert in the Hawai'i Theatre, a treasure of a building restored to its 1920s splendor, brought acoustics back into the foreground.

Led by guest conductor Julian Wachner and pared to fewer than 50 musicians, the orchestra presented Haydn and Beethoven as they cannot be heard in the Blaisdell Concert Hall.

In some ways, the Hawai'i Theatre provided a more "authentic" performance: The smaller orchestra was closer to the sizes used by Haydn and Beethoven, but it sounded large because of the space. The building's smaller size, higher, shallower seating, and ornate decor recalls the ambience of older European halls. Even Concert Conversations afterward, held in a long, narrow reception room, felt 19th-century-ish: intimate, with musicians in tuxedos standing around. And that intimacy prompted more questions and discussion than ever before. It's a pity the Blaisdell lacks something similar.

The music sounded unmixed, almost raw, as though the audience was seated amid the orchestra, hearing independent lines from all directions, instead of in that homogenized blend so emblematic of modern orchestras. The orchestra's sound in the theater underscored inner lines and secondary parts, which can so easily blend into oblivion in a larger hall.

That, at least, is how it sounded in the loge. In a hall such as the Hawai'i Theatre, sound can change dramatically depending on where one is seated.

The orchestra's Hawai'i Theatre sound was at its best in Beethoven's "Egmont" Overture, and especially in Haydn's "London" Symphony, No. 104. Wachner presented clean, well-balanced and well-thought-out interpretations that were exciting and engaging.

The strings reigned supreme, thanks to the section chairs: Ignace Jang, concertmaster; Hung Wu, second violins; Mark Butin, violas; Mark Votapek, cellos; and Kirby Nunez, basses. Of particular note among the wind solos was Paul Barrett's tasteful support of the strings in the second movement of the Haydn.

The theater was least kind to Beethoven's C Major Mass, which squeezed orchestra, chorus, soloists and conductor onto a stage designed for half as many, with the soloists literally tripping on and off for bows. The Honolulu Symphony Chorus, capable of rattling fortissimos in the much larger Blaisdell hall, sounded good but lost most of its power into the fly space above the stage.

After the concert, Wachner commented on how difficult it was for the musicians — orchestral and choral — to hear: "There were many, many challenges: listening in a different way, and being so cramped. It doesn't sound good on stage, but it sounds good in the (hall). If there had been a shell, that might have helped."

Whatever the orchestra's struggles, the sound in the hall was different but good. In some ways, it was even better than the larger, more blended sound in the Blaisdell. Especially loved passages included the "Deum de Deo, lumen de lumine" section of the "Credo"; the opening of "Gloria"; the sibilant entrances in the opening of of "Sanctus"; and a clarinet solo by James Moffitt.

The evening's glory turned out to be mezzo-soprano Laura Vlasak Nolen. Remember that name; you will probably hear it frequently in the future. Her voice was, quite simply, stunning: large, rich, warm butterscotch, beautifully placed. If Beethoven had known she was going to sing, he would have composed an extra movement just for her.