On September 13th, Apple released iTunes 12.5.1. It works in El Capitan but has some new features that make it macOS Sierra ready and provide support for iOS 10. Most notable is a fresher, cleaner look.
Apple’s release notes say:
There an all new music design which brings greater clarity and simplicity to every aspect of the experience.
Support for iOS 10.
Support for SIri in Sierra. Just ask Siri to play a song
Picture-in-picture. Watch videos as you multitask and use different apps.
Apple has been updating iTunes at a regular pace since version 12 was released. This new visual and operational simplification goes a long way towards addressing the criticism of the original version 12 release which was considered non-intuiitive, complex and visually busy.