Today's St. Louis Chamber Chorus concert, "Music of the Fall," marks the second during artistic director Philip Barnes' sabbatical season in England. It's also the first in which other conductors will provide leadership on the podium.

Guest conductor is Kathryn Smith Bowers, a music professor and director of choral activities at Webster University. She and her husband, Dave, have long worked as volunteers for the Chamber Chorus, but this will be her first time leading it.

Bowers will share those duties with SLCC assistant conductor Orin Johnson, who has done the rehearsal preparation.

"It's a different experience for me," she says. Some guest conductors "have set ideas about how they want things to sound, and they start by getting up and talking a lot about it. It makes more sense to me to just dive into the music, and find out where they're at."

Bowers isn't too worried about this choir, in any case.

"I'm going to have wonderful material to work with," she said. "I would hope that it feels collaborative for them. The conductor has to be willing to do what works for the ensemble."

Johnson and Bowers have an ambitious program. It includes German Late Romantic composer Max Reger's monumental "Drei Motetten (Three Motets)," which are so difficult that they're virtually never sung in their entirety. That makes this an important concert for anyone with an interest in choral music.

Bowers initially suggested to Barnes that the Chamber Chorus sing the third motet. He agreed enthusiastically, and then decided that they should collect the whole set.

"And the other two are twice as long and twice as hard as the third one," she said — about 15 minutes each to No. 3's eight minutes.

Bowers will conduct the first and third of the motets; her choir, the Webster University Chorale, will join the Chamber Chorus on the last. They'll also sing a pair of Hungarian motets and Henry Purcell's "Funeral Sentences."

Also on the program are a 17th century Lutheran Mass, based on the traditional tune "On Adam's Fall," and a world premiere by Chamber Chorus composer-in-residence Clare Maclean, "Slow Gold," with words by Emily Dickinson, John Bunyan and Psalm 23.

The venue is the still-new Community Music School of Webster University, a 500-seat space with a good acoustic.

This is Bowers' 24th year as a full-time professor at Webster, and it will be her last: She'll officially retire next spring. She says she'll continue to teach "on a part-time basis. I'm still hoping to get my 25-year chair" (a special chair with the school's seal on it, given to professors who teach for a quarter-century).

A native of Arkansas City, Kan., Bowers plans to spend more time at the couple's condominium in Estes Park, Colo., and traveling.

"There's still an awful lot I haven't seen," she said.