SUFJAN STEVENS: It was exciting and weird. I’m familiar with Justin’s language, but there is stuff in here that I’m surprised to see. His way of breaking down the measures is really different than mine.

MULLEN: This is your first piano-only score. Why did you decide to go in that direction?

STEVENS: I wanted to simplify it, because the last ballet we collaborated on, Everywhere We Go, was a full orchestra and it was almost 40 minutes. It was kind of power pop and really, really dynamic and celebratory and unabashedly fun. This time around I wanted to be more pensive and more cerebral, and less explicitly harmonic and melodic. So I kept it with the piano because the piano lends itself to lots of harmonic discursions, and you can get away with a lot on it. A lot of the score is based on impromptu improvisations that I’ve developed over time. I collected about 50 of those ideas and spent maybe three weeks reducing it to the score that it is now. For Everywhere We Go I spent months, and it was really back and forth with Justin, who curated some of it, whereas this time around I finished the draft of the score, gave it to him, and it was maybe 80 percent there.

MULLEN: How was it different for you, Justin, coming in later to the process?

JUSTIN PECK: I can only really do it with someone that I trust, and I’ve worked a lot with Sufjan, so I felt comfortable going about it that way. It was kind of nice, actually, because you’re handed an entire ballet score and it’s like a Christmas morning present, getting to sit down and listen to it and get to know it. It was interesting to see Sufjan’s music take a step in a different direction, and I think it’s going to be something that people don’t necessarily expect, in a good way. I think it shows more range for what Sufjan can write, and there’s already so much range to begin with.

MULLEN: Sufjan described the music as more thoughtful and contemplative. How would you describe the movements?

PECK: I would say reverent. It has this post-modern or 20th-century ballet feel to it. I find little similarities to Paul Hindemith, especially the score he wrote for The Four Temperaments. It’s got an interesting structure and fluctuation. The ballet ends is the same way that it starts, which was Sufjan’s idea. There was this great moment when we made that in the studio—which was like, yesterday, by the way [laughs]—where it ends with them bowing towards Susan [the pianist]. We didn’t intend for that to happen, but the dancers were like, “Oh, look, we’re bowing towards the pianist.” It’s got this nice feeling of respect.

STEVENS: It does seem like this ballet is as much about the pianist as it is the dancers.