It wasn't that long ago that Apple updated iTunes to take advantage of its new Apple Music service. The latest update fixes a bug with that exact service.
iTunes 12.2.1 was released overnight as a free download. The core bug that it's addressing relates to iTunes Match customers. Specifically a bug may have identified iTunes Match content as being Apple Music content, which meant that they'd have layers of DRM added even if they were actually serving DRM free files.
In addition, some iTunes Match customers were incorrectly blocked from accessing Apple Music at all. It's also stated to include minor bug fixes and "improvements for Beats 1", although it's unclear how you bug fix an online radio station.