The phone is not a telescope. You don't point it at the sky or hold it up to anything. The piece starts as soon as you grant location access, and you can put the phone in your pocket. The listening happens in your ears.
Find a comfortable place. Sit, stand, or walk. The chord is steady enough that you can move around without losing it.
Any headphones work. The chord, the tuning, and the sky's slow rotation come through on whatever you have.
What unlocks the full spatial design is head-tracked spatial audio, available on AirPods Pro, AirPods Max, and AirPods 4 with Active Noise Cancellation. With those, the cosmos stays anchored to the world as you turn your head. A star you hear behind you stays behind you when you look the other way, the same way a real star would.
Wired earbuds and other wireless headphones still give you the spatial chord, but it moves with your head instead of staying anchored.
Speakers in a room work too. The chord and tuning are intact. The spatial design flattens, since the per-ear cues that place a star above or behind you depend on each ear hearing something slightly different.
The cosmos has to be oriented somehow. By default, whichever direction you happen to be facing when the piece starts becomes the front of the piece. The chord is correct, but you don't know which star is which without checking the actual sky.
To line the piece up with true compass directions, so a star to your east in the audio is actually east in the sky, use the compass button.
compass appears once the piece is playing. Tap it, hold the phone still for a few seconds while it samples your heading, and the cosmos rotates to align with true north.
calibrate is the same button, renamed after you've used it once. Tap it any time things feel off, after you've moved a lot or turned around without your headphones, and it re-runs the alignment.
You don't have to use either. They're there if you want to know where you're listening from.
The piece moves slowly. Sit with it for at least ten minutes. The chord changes as the Earth turns, but a single star moves too gradually to notice over the course of a minute. Over an hour, you'll hear that the western voices are gone and the eastern ones have come up.
Daytime is mostly silence. The Sun overwhelms the visible sky and the piece honors that. The Moon and the brightest planets stay audible during the day if they are far enough from the Sun.
Twilight is the most active window. As the sun drops below the horizon, the stars rise gradually through civil twilight, only reaching their full strength when the sky is genuinely dark. The same fade plays in reverse at dawn.
For more on what the piece is and what to listen for, see the about page.
Lock the phone, put it in your pocket, take a walk. The audio keeps playing. Lock-screen play and pause work, as do the controls on your AirPods.
If another app interrupts (a phone call, a video, a notification with sound), the piece pauses for the interruption and resumes after.