Ludwig van Beethoven has a sobering effect on musicians and composers that seemly equals the power he wields over listeners. He spooked Johannes Brahms so decidedly that he waited till later in life to publish his first symphony and his first string quartets. Many a musician's career has been judged by the handling of the Romantic composer's influential scores. And his music can make everything else in a concert seem frivolous.

Witness the Orion String Quartet's appearance Monday night at Carnegie Music Hall in Oakland.

The world-renowned ensemble has two members hailing from Squirrel Hill -- violinists and brothers Daniel and Todd Phillips -- and decades of accrued experience. The concert that opened the Pittsburgh Chamber Music Society series found the group starting with a beloved bit from Bach's "The Art of Fugue," followed by Webern's "Five Movements for String Quartet" that is more fun to play than to hear, and then closing with Brahms' upbeat String Quartet in B-flat Major.

From opening to intermission, it certainly appeared that, despite the infamous stuffy conditions of the hall on a warm day, the Orion members were enjoying their latest return to Pittsburgh. The Bach (Contrapunctus I) arrived impossibly refined, a reading of the Webern miniatures emphasized the sonic pleasures of the sound effects, and an effusive playing of the Brahms quartet (with Todd at the lead instead of Daniel) was a labor of love with out any laboring.

But then Beethoven's C-sharp Major Quartet, Opus 131, landed.

You should know off the bat that any Beethoven work with an opus (largely his own designated) catalog number in the triple digits is holy in classical music. It's what musicologists call Beethoven's late period (he lived from 1770-1827), a rarefied group headlined by the Ninth Symphony (Op. 125), the late piano sonatas (Ops. 109-11) and the "Grosse Fuge" (Op. 133).