If you want to play iTunes music on non-Apple devices, you have to remove DRM protection at first. All iTunes Audios are encrypted with DRM protection, it can be played on Apple devices only. Fortunately, there are many DRM removal tool for us to remove DRM protection and convert iTunes audios from M4P to common MP3, AAC, M4A, M4B, etc. The tool for me is
DRM Audio Converter for Mac. It is designed to convert DRM protected Audios at 30x faster speed with no quality loss. Good luck to you.
Learn more:
Convert iTunes movies from M4V to MP4