Spatial Music is an iOS app that uses Apple's motion tracking and 3D rendering APIs to play music in 3D space.
This app uses the motion tracking hardware in AirPods Pro, and won't work without them.
It should be noted that this app is a work-in-progress. It doesn't support all the features you'd expect from a normal music player, including the ability to queue songs. It can also only play DRM-free songs, which means no music from Apple Music.
This project was more intended as an exploration of iOS, motion tracking, and 3D rendering, both visual and aural.