Donald Nally, 50, founded the Crossing, an unusual, fully professional chamber choir in Philadelphia, in 2005. The acclaimed group cultivates composers who take choral singing in totally unheard-of directions. In its June festival in Chestnut Hill, the Crossing will perform four world premieres, along with works written in the last 15 years. Inquirer music critic David Patrick Stearns spoke with Nally, who is moving back to Philadelphia to work more closely with his creation.

Question: You're leaving your position as chorus master at the Lyric Opera of Chicago. Though you were preparing choruses for performances that others would conduct, the Chicago job was among the best of its kind. Why are you returning to Philadelphia?

Donald Nally: Carmen is a great opera, but seven or eight times is enough. I don't need to do another one of those. I love doing a variety of things, and I want to have more control over my own repertoire. I'm doing what I want to do. The Crossing isn't going to pay me a living. Maybe someday. Maybe it'll close its doors after a few seasons.

Q: That's not likely as long as the Philadelphia Music Project is giving you grants up to $70,000, which it did for your 2013 season. How will you use it?

Nally: We're pinching ourselves to see if we're still alive! The project is named the Gulf Between You and Me. It's taking the Gulf of Mexico oil-spill tragedy, but also drawing parallels between our inability to communicate with each other and listen to what the Earth is telling us. So the gap between us and a healthy Earth just gets larger and larger.

Q: That's a heady concept - but then all of your festivals have them.

Nally: I don't want to sound like we're trying to educate anybody. I'm not interested in producing art that challenges the audience. We're strictly about singing the best music that's being written today and hopefully commissioning some of it.

Q: The ancient Roman philosopher and playwright Seneca is the theme of your 2011 festival. What relevance does he have to us?

Nally: We're trying to explore something contemporaneous to Christ, but something that isn't Christ. There are passages in Shakespeare that are basically rewritten Seneca. I don't think there could've been a Macbeth or Hamlet without Seneca's worldview or influence. It says, "Yes, there is a god, but I'm hopeless nonetheless." The composers we have are so different from each other. If you put those cats in a room, would any come out alive? The Crossing is interested in finding out what their voices will bring to Seneca's profound words.

Q: One of your composers is the celebrated young Latvian Eriks Esenvalds. What's he up to?

Nally: Eriks has focused on this idea of the zodiac falling out of the sky and into the sea. He's such a nerd! At certain moments, he has drawn the constellation in the score connecting certain pitches that he calculated to be part of the constellation - to draw a crab or a goat or a scorpion or whatever. You won't hear it. It passes by you. It's our little secret.

Q: Some of the composers are overtly religious, such as local composer Kile Smith; others not. My guess is that we might not be able to hear that difference. Does the creative process, which is probably spiritual in itself, circumvent religious beliefs?

Nally: When I was in Cincinnati conducting Vocal Arts Ensemble, I was asked by the wife of a board member, "Are you a man of faith?" I was a little shocked. I said, "Did you feel that the concert had spirituality?" She said that it was an amazing spiritual event. And I am not a man of faith. But that doesn't affect how I live my life or make my art.

Q: You'll be knee deep in religious music this summer in Riga, where you're conducting the great Latvian State Choir as part of its annual Sacred Music Festival.

Nally: It's opening with me! I was asked for a concert of American sacred music: 'What are the pieces you'd like to take that you love and want to share with them?' It's really tough. So I wound up with a very strange program. [Pulitzer Prize-winning composer] David Lang has this piece based on Genesis, Evening, Morning Day. He loves to take these Old Testament texts and rip them down to where they're just the essence, only these catchwords that lead you out of the context but with enormous content. The concert will end with his Again, an Ecclesiastes text, a very beautiful piece that repeats this loop over and over until you get into this atmosphere of timelessness.

Q: Though this isn't an engagement for the Crossing, did it come about through your work with the group?

Nally: I think it came through Eriks. He's done a lot of listening to our group, what I can and can't do, and decided that we can do a lot.