Jim Dalrymple has written an update about the state of his music collection, post-Apple Music. As part of it, he includes some information on upcoming fixes for the service. From The Loop:

The missing and duplicate song issues that we've all seen in Apple Music are being fixed shortly. They are certainly aware of what's been going on, I can assure you.

In hindsight it looks like it would have been better for iTunes to preserve existing libraries in their original state and apply Apple Music almost like delta files—a separate list of changes that get presented on top of the original library. Something akin to how edits are handled in Photos.

I have no idea how complex that would be, of course, but when dealing with things that have deep and deserved emotional attachments, like music or photo libraries, not touching it directly seems prudent.

New stuff, sure. Build that from scratch the modern way. Old stuff, keep it safe at all costs.

As to Jim's collection:

It's been an interesting and confusing day. I arrived at Apple this morning to talk to them about my issues with Apple Music and to hopefully fix my problems. The good news is that I have about 99 percent of my music back.

Luckily, it looks like most, though not all of it, was recoverable from iTunes Match.

Great news for Jim and, hopefully soon, for everyone.