Piano Portal Jam
Open a portal to Karel's real piano and send it to a friend with one link. Then play it together — peer-to-peer, two constellations meeting.
His whole performance is loaded as a corpus of sound-grains. Tap and drag the field to re-sound it. Leave it alone and a ghost player drifts a duet with you. Open a portal to play it with a real second phone.
Best with headphones. iOS needs this first tap to start sound.