How to upgrade iTunes music to remove DRM encoder
In the past, iTunes purchased music was copy-protected using a form of Digital Rights Management (DRM) called FairPlay, and was not playable on non-Apple devices, including Sonos.
Apple no longer sells DRM protected music and all music now for sale is free of any playback restrictions. If you still have some tracks that are DRM protected and unplayable on Sonos, iTunes Match allows you to upgrade your music to a DRM-free version. More information on iTunes Match and instructions on upgrading to DRM-free can be found on Apple’s website.