Yes, iCloud Music Library has metadata-matching issues, but you don't need to panic

Earlier this week, Kirk McElhearn posted a rather-worrying article about iCloud Music Library's "matching" algorithms.

As you might know, Apple offers the iCloud Music Library service as part of Apple Music and iTunes Match. This scans your Mac's music library and attempts to do two things: "match" tracks in your library with songs in the Apple Music or iTunes Store catalog (which catalog depends on which service you're subscribed to), and upload songs it can't match directly to iCloud.

From McElhearn:

If you've used iTunes Match in the past, you may know that it matches music using acoustic fingerprinting, which means that iTunes scans the music, and matches it to the same music. It doesn't matter what tags files have: you could have, say, a Grateful Dead song labeled as a song by 50 Cent, and iTunes Match will match the Grateful Dead song correctly...Apple Music, however, works differently. It does not use the more onerous (in time and processing power) acoustic fingerprinting technique, but simply uses the tags your files contain. And it can lead to errors.

This means that by changing metadata on a track, you may be able to "fool" Apple Music into matching it with a different track in your iCloud Music Library.

Does this suck? Yep. It's also likely a bug, and I have no doubt that the folks at Apple are well aware of it and working hard to make sure it happens as infrequently as possible—preferably not at all.

I can't reproduce it in my iTunes Match/AM hybrid library, or my boyfriend's Apple Music-only library

I have both an iTunes Match and Apple Music subscription, and decided to duplicate McElhearn's testing to see if I could get the same results. Answer: Not really.

I used my auxiliary MacBook Pro which has a handful of local songs; most are stored in iCloud Music Library, matched with my desktop iMac.

I did this test three times for both a matched and uploaded track: First, I saved a copy of an AC/DC track that iTunes Match had matched to my desktop and reuploaded it to iTunes as The Weeknd's "Can't Feel My Face"; upon local deletion and redownload, the track remained AC/DC's music, though it kept the erroneous metadata I'd assigned it.

For the uploaded track, I added a 7-minute voice test I did for The Incomparable Radio Theatre on the Air, and labeled it as Foreigner's Juke Box Hero. Interestingly, when I first uploaded the track to iCloud, it very briefly matched as Apple Music; when I deleted it from my hard drive, however, the track reverted to showing as "Uploaded" in my iTunes library, and upon redownload, played the same 7-minute test as before. On redownload I did get pretty Foreigner album art, however.

Update: I also ran these tests three times on my boyfriend's Apple Music-only library, with both an uploaded Incomparable track and an Apple Music-matched Billy Joel song (trying to transform it into a Weeknd song). No mis-matching.

What does this mean?

Likely what I've been saying about Apple Music, iCloud Music Library, and Match from the start: Matching tracks is hard, and if you're trying to trick a complicated system, or have unique tracks that Apple's never scanned before, you're likely not going to be too happy. Unfortunately, I suspect this is the nature of the matching game—doing this on such a large scale requires active user testing, and that means bugs and mistakes.

From my tests, it looks as though Apple is still using acoustic fingerprinting for iTunes Match accounts, but may be augmenting this with metadata matching for Apple Music. I wouldn't be surprised if, due to the whole "having to connect to the Internet" thing, Apple Music's metadata matching occasionally happens before iTunes Match's fingerprinting; if you happen to immediately delete your track as it's processing, you may wind up accidentally with an Apple Music track.

And yes: On this, Apple has failed. iCloud Photo Library was very smartly released as a beta, because of similar syncing issues and testing that needed to happen. iCloud Music Library wasn't, nor was it released with comprehensive documentation or even a warning to back up before upgrading. As a result, quite a few people have seen their home music libraries show up as bizarro copies on their auxiliary devices; those who don't have backups are even worse off.

That's devastating to both users and Apple. There are so many great things about iCloud Music Library and Apple Music, but right now, they're getting overwhelmed on social media and in the press by users having serious issues with their libraries and apps. Songs that mis-match, albums that won't download, buttons that don't work. Every time the service errors, people feel less-inclined to trust Apple with their cloud data, and consider alternatives that may be more stable, but not as secure. It's a shame.

I'm nervous now. Should I not use iCloud Music Library?

That largely depends on your library and what's in it. If you mostly have purchased tracks and ripped songs from studio albums, you should be fine with iCloud Music Library—but make a backup just in case. Remember: iCloud Music Library is, ultimately, making a secondary copy with its matching and uploading. You'll get these matched and uploaded copies when you download tracks on secondary devices, but it shouldn't mess with tracks local to your hard drive. And please: Do not use iCloud Music Library as your backup. It was never designed as a backup service.

Shouldn't and doesn't, however, are two different things, and as I said before—matching is hard. So if you have a history of problems with your Mac's iTunes library and you're concerned about iCloud Music Library messing up your tracks, it's simple: Just don't use it.

For those that are having problems—either matching or otherwise—turning off iCloud Music Library and restoring from a local backup of your music should bring everything back to normal. I made a really handy guide last week for people who want to use Apple Music without iCloud Music Library, which details a few different ways you can set up your devices to prevent your primary library from getting screwed up.

Still concerned?

Make a backup. Turn off iCloud Music Library. Check our our troubleshooting guide. Call Apple. Or ping us in the comments if you're confused about this whole thing and this didn't help straighten it out.

Updated 2:07PM EDT to add tests on an AM-only library.

Serenity was formerly the Managing Editor at iMore, and now works for Apple. She's been talking, writing about, and tinkering with Apple products since she was old enough to double-click. In her spare time, she sketches, sings, and in her secret superhero life, plays roller derby. Follow her on Twitter @settern.

15 Comments
  • I'm not gonna lie, when I saw Marco RT that post, I wanted to shut off all things Apple Music and reconsider going back to Spotify. But I'm already matched up to the cloud, so I don't know if I avoided the problem or if it is still possible that match data could change. This is pretty worrisome knowing my library could (once again*) get screwed. *-long story for another time
  • As long as you've got a backup of your local tunes, you should be fine! (And if you don't have one, make one now. :)
  • A backup is the only way I averted a Dalrymple level disaster the first time I synced.
  • Yesterday, I went on some errands and turned on my music app on my iPhone and all my playlists and music was gone. It looks like I turned on a feature on iTunes iCloud Music Library. This turned removed my music from all my devices until I turned on the feature on each device. Of course, you can only do this while on a wifi connection. When is Apple going to redo iTunes, this needs to happen soon.
  • I wish I had known about these issues before I signed up for a trial for Apple Music, yet I'm not 100% sure that iTunes Match wouldn't still be messed up if I chose not to sign up. This is just very unpredictable and has cause a bit of issues matching new music that I bought. iTunes match isn't perfect and never really was, but it was very convenient. I still like the service sans the Apple Music take-over, but for a person who has almost 25,000 tracks, it just seems like I need to rush and make another back-up just in case something really terrible happens.
  • For my CD rips, I've taken to renaming songs to include the name of the album to make sure I don't get "single" mixes when I should get an album mix (which sometimes can differ oh so slightly) or god forbid, get a full version of a track in the middle of a DJ mix when it should be that release's particular blending! So far, so good.
    The match should be a combination of fingerprinting, song title, artist, and RELEASE, as well!
  • Apparently, Apple Music doesn't use acoustic fingerprinting:
    http://www.mcelhearn.com/apple-music-matches-files-with-metadata-only-no...
  • If you have os X and ios devices, my advice is to enable iCloud Music Library on an ios device first. If things go wrong, you can always disable it and sync your device to iTunes for a complete library restore. I have a rather small (5 Gig) but meticulously tagged music library. Both times I tried enabling iCloud Music Library, I got several erroneous tags and artwork plus a few missing/duplicate songs. If it weren't for Time Machine, my library would be lost forever. Until these problems are resolved, I'll keep iCloud Music Library disabled on ALL my devices although doing so greatly reduces Apple Music functionality.
  • I have both iTunes Match and Apple Music, I noticed erroneous album art and a few missing tunes I owned. I had a back up so was not overly concerned. However it appears the gaps and album art are now okay. This occurred gradually over the last couple of weeks.
  • Strangely enough, all of my computers and my iPhone are showing the same amount of songs in both my music and Apple music, my iPad does not. Maybe it's just a bug (its on iOS 9 beta) although, my iPhone is as well and it shows the correct amount of songs. I did find where there are two less Megadeth songs (from a 3-song EP) on my iPad than everywhere else? Why? iCloud Library is iCloud Library everywhere or is it? I am sure if I kept looking, I'd find other instances like this one as my iPad is showing 40 less songs than the newly setup iTunes on Windows, my main iTunes, and the iTunes on my Macbook Pro as well as iPhone. This is baffling, and I just can't figure it out. The number of Apple music songs is the same, just not the amount of my music. Interestingly enough, these two songs were purchased from the iTunes store, not rips. They are identical duplicates of songs released later as part of an album. I have almost given up trying to figure this issue out and wait on the next iOS 9 beta to see if that fixes my issue.
  • At 1st my MacBook won't do Match after the July 13th update but my iMac was doing Match ok. So I called Apple Support Care. The tech had me do somethings then iTunes Match wouldn't work on my MacBook OR my iMac (but still worked on my iPhone 5s). He said they maybe - maybe would do a fix-me update about it and to just use Apple Music. Of course all my CDs I loaded onto iTunes Match when it 1st came out are now toast in that I can't use them on my iPhones. I called again today and another tech was not as encouraging. I was basically told it's a good thing I back up my hard drives and that the yearly subscription I just updated in April --- I got ripped off and too bad for me.
  • Has there ever been an Apple release that has required more instructional and informational articles than Apple Music? Should it really be that complicated to use properly?
  • I like this post. Helped me a lot.
  • It just works! Posted via the iMore App for Android
  • Ugh. I've been a late adopter to Apple Music and I've encountered this problem in spades. The issue is not so much about mislabeling tracks, it's about Apple Music not being able to distinguish between different versions of a track with the same name. Note that in my situation I have never had iTunes Match. I subscribed to Apple Music's three month trial and set up iCloud Music Library on my Mac and iPhone. Initially iTunes was still syncing tracks from my Mac to my iPhone, but recently all the music on my phone was deleted (sometimes this happens if my Mac's external drive -- where my music files are stored -- is disconnected) and syncing wasn't working anymore. So I proceeded to download tracks to my iPhone from my iCloud Music Library. So far so good (although it seems a needless waste of bandwidth for me to have to download all my music again). Once I finished downloading the music I began to notice the problem. If you have two tracks with the same name by the same artist on different albums, Apple Music will usually not distinguish between them. This occurred most often for me with a 'live' album -- if the track name from the live album is the same as the name of the track on the studio album, Apple Music has downloaded the studio version on my iPhone virtually every time. When iCloud Music Library uploaded my music from iTunes, it matched my live tracks with the studio versions. Now there is a fix -- you have to re-name the live version (eg. "Song Name [live]"), then delete it from your music library, re-add the file from your hard drive to iTunes, and now iTunes will upload the correct version of the song. Delete the download from your iPhone and re-download the song to get the correct version. Other than the sheer amount of time it would take to do this for every affected song, the other problem with this solution is that removing the file from your music library also removes it from all of your manual playlists, and it also wipes the play count and ratings info for that track when you re-add it to iTunes. This is too much of a hassle for me. I'm bailing out of iCloud Music Library until Apple has a better fix (eg. surely they could provide an option in iTunes to force upload the song or force match with acoustic fingerprinting?)