It sounds like Apple is about to launch its previously announced Spatial Audio feature for Apple Music. The feature could be announced at a separate event that takes place right after Apple's developer conference keynote.

The event seems to gave been leaked by a video posted on Reddit and reported by MacRumors. The time of the event seems to be 12pm PT, so two hours after the start of the standard keynote.  

The enhancement to Apple Music was announced alongside lossless audio but while millions of tracks will be available in lossless quality, the Spatial Audio tracks will only be in the thousands. Only certain devices are compatible with spatial audio and/or Apple Music lossless. 

Spatial Audio uses Dolby Atmos technology and will automatically play Spatial Audio-enhanced tracks on all AirPods and Beats headphones with an H1 or W1 chip.

Spatial Audio will also work with the built-in speakers in the latest versions of iPhone, iPad, and Mac devices, though don't expect an iPhone's speaker to suddenly sound amazing because of the technology. The HomePod range will also support it with an update. 

Devices will need to be running at least iOS 14.6, iPadOS 14.6, macOS 11.4 or tvOS 14.6 or later. 

Apple's Worldwide Developers Conference (WWDC) takes place between now and 11 June 2021. The opening keynote takes place today at 10am (PDT), 1pm (EDT), 6pm (BST).