Keeping Your Music Tags Intact When Converting a Library

You convert an album, open it in your music player, and find a folder of tracks by "Unknown Artist" on an album called "Unknown Album", with no cover art. The audio is perfect. The metadata is gone.

This is common when converting between formats, and it is worth understanding — partly to set expectations, and mostly because the fix is faster and better than trying to prevent it.

Why tags do not always survive

Audio metadata is not stored the same way in every format. MP3 uses ID3 tags, a standard bolted on years after MP3 itself and existing in several incompatible versions. WMA uses Microsoft's ASF metadata objects. M4A uses Apple's atom structure. FLAC uses Vorbis comments. WAV barely has a metadata system at all.

These schemes do not map onto each other cleanly. Some fields have obvious equivalents — artist, title, album — while others do not exist on both sides. Cover art in particular is stored quite differently and frequently fails to transfer. Non-Latin characters can also come across mangled where the two formats disagree about text encoding.

WMA is a particularly awkward source, both because its metadata model is furthest from ID3 and because Windows Media Player wrote its own extended fields that nothing else recognises.

What always survives

Filenames and folder structure. Converting changes only the extension, so 03 The Chain.wma becomes 03 The Chain.mp3 and stays exactly where it was in the folder hierarchy.

This matters more than it sounds, because a library ripped in Windows Media Player almost always has meaningful structure: Artist/Album/NN Track Title. That structure alone is enough for a tagger to work from, and enough for you to navigate manually if you never get round to re-tagging.

The better fix: re-tag afterwards

Rather than trying to nurse imperfect metadata through the conversion, convert everything first and then re-tag in one pass. The tool for this is MusicBrainz Picard — free, open source, and available for Windows, Mac and Linux.

Picard's advantage is that it does not rely on existing tags at all. It calculates an acoustic fingerprint of each track, matches that against a large community database, and fills in artist, album, track number, year, genre and cover art from the match. It works even when the file has no metadata whatsoever, and it is generally more accurate than what was in your WMA files to begin with — those were filled in by Windows Media Player from a database that has not been updated in fifteen years.

The workflow is straightforward: convert your library with the WMA to MP3 converter, point Picard at the output folder, let it scan, review the matches it proposes, and save. A few hundred albums takes an hour or so, most of which is unattended.

Alternatives worth knowing

Mp3tag (Windows, with a Mac version) is excellent for bulk manual editing — renaming fields across hundreds of files, deriving tags from filenames, or applying a consistent album artist. It is the right tool when your filenames are good and you simply want them turned into tags.

Your music player. iTunes/Music, MusicBee and foobar2000 can all look up metadata and edit it in bulk. Convenient if you are importing anyway, though usually less thorough than Picard.

Manual editing is fine for a handful of albums that matter and unbearable for a library. Reserve it for the ones the fingerprinting missed — usually live recordings, bootlegs and obscure releases.

Do it in the right order

Convert first, tag second. Tagging before conversion wastes the work, since the tags may not survive the format change anyway. Tagging after means you do it once, on the files you are actually going to keep.

It also means you can do the whole library in a single pass rather than album by album, which is a substantially better use of an evening. The library rescue plan puts this step in context alongside auditing, converting and verifying.

If you are archiving rather than listening

Format choice affects how well tags hold up long-term. FLAC has clean, well-specified metadata support and handles cover art properly, which is one of the reasons it is the standard archival format. MP3's ID3 tags are messier but universally understood. WAV is the worst of the three for metadata and should be treated as a working format only, not a place to store a library.

If the plan is a permanent archive, FLAC plus a proper tagging pass is the combination that will still make sense in a decade. The bitrate guide covers when your source files justify going lossless.

The short version

Expect tags to be unreliable across a format change and filenames to be reliable. Convert the whole library first, then run MusicBrainz Picard over the results once. You will end up with better metadata than you started with, and you will spend less time on it than trying to preserve the old tags would have taken.

Start with the converter, or read the step-by-step guide if you have not converted anything yet.