Can't rip CD into my Son's iPod because of Apple Music
As I suspected, once you turn iCloud library on, it is reluctant to allow you to add music using iTunes alone, as there could be file duplicates and a storage war. 

Per Apple's forums, turning off iCloud musing will allow you to sync music manually, then you can turn it back on. Note this will delete all the 'iClouded' music and then re-download it, you you'll probably want to do this when you have a spare hour or so and a stable wifi connection.