Planetarium is the new collaborative album co-composed by Sufjan Stevens, Bryce Dessner, Nico Muhly and James McAlister. A completely reimagined version of the project originally undertaken years ago and performed in various iterations around the world, Planetarium unites Stevens' vocals, McAlister's beats, Dessner's guitar performance, and Muhly's instrumental compositions – part rock odyssey, part electronic experiment, part classical opus. Conceptually, Planetarium revolves around the cosmic ideas Stevens' lyrics explore: mythology, astrology, science, astronomy and the intricacies of human consciousness.

The album began when Dutch concert hall Muziekgebouw Eindhoven commissioned Muhly to create a new piece and he enlisted friends Dessner, Stevens and McAlister, all of whom had been looking for the opportunity to collaborate on a larger scale. After sketching the framework of the song cycle and performing the piece as a band – flanked by a string quartet and seven trombones – in various forms, the quartet put the project on hold for several years. Returning to the raw material in 2016, Stevens and McAlister reversed their typical process, taking recordings of the live show and adapting to the studio.

"We had recorded all the arrangements and the live parts in a studio after our last performance," says Stevens, "so years later when we all kind of settled down, we said, ‘let's open Pandora's box.'" Stevens and McAlister worked to arrange Muhly's symphonic framework and Dessner's guitar virtuosity alongside their own lyrics and beats. Stevens became the driver behind the "song" part of the song cycle, his unique voice providing a clear and coherent center of gravity for the whole project.