you are the point directly below
nothing here was composed
The nadir is the point on the ground directly beneath a satellite — the place it is passing over. The name is written from orbit looking down, which means the visitor is the nadir. You are the point directly below.
Around four hundred real satellites are overhead right now, propagated from element sets published by CelesTrak. When one crosses a circle drawn around a city, that city sounds. Three concentric bands step the pitch up as it works toward the centre, and the loudest note of any pass is its closest approach — predicted ahead of time, not noticed afterwards.
Which cities you choose is the composition. The spread of their latitudes picks the mode and the tempo; a tight cluster is slow and pentatonic, a continent-wide selection is faster and Lydian. The spread of their longitudes sets the size of the room, from a small space to a large slow one. How far east they sit lifts the root by up to ten semitones. Two cities within three hundred kilometres stop being separate voices and become one, the lower an echo of the higher.
Nothing here was composed. There is no recording, no sequence and no random number generator. Every note is the arithmetic of an orbit, and the piece has never played the same way twice.
Elements from CelesTrak · coastlines from Natural Earth · after trainjazz.com