I have just discovered (the hard way!) that if you purchase music from the iTunes store, either individual tracks or a complete album, and Apple choose to delete the album the tracks were on or the complete album, your purchased music will no longer play!
The advice I received from Apple was: if the tracks are available on other albums, by that artist, buy them again! Having fallen for it once, I'm not about to fall for it again.
Thanks for that Mick, very useful to know. I'm sorry you learned the hard way. Presumably the licence let's them do that (I know it's not a straightforward sale even though we always talk about "buying" it).
On a related note (B sharp?), has anyone with ripped CDs in their library subsequently taken a subscription to Apple Music (ie pay monthly to stream whatever you want)? I keep being offered free trials but see it as risky.
When the service was new, a number of people found that it wiped any pre-existing copies (notably ripped CDs) in their library. My library is mostly ripped from my CDs, the ripping/metadata process is a huge investment of time that I would hate to lose; it was damaged even when Music was updated some years ago.
All very alarming! Like Tony, most of my music is ripped from CDs (or from vinyl / cassette!). Fortunately it is all copied onto a couple of USB sticks inserted in the front of Yamaha hifi units.