However these new fields have caused a problem.
Why is my grouping column blank for newly imported files ?
MP3 and AIFF files use the ID3 metadata format for storing information about the music such as the artist or album name. ID3 did not have any fields (known as frames) defined for most of these new fields so Apple has defined some:
MVNM - Movement
MVIN - MovementNo/MovementTotal
But ID3 does already have a field that could possibly be used for storing the work, the TIT1 frame, this is how it is defined in the ID3 specification document.
The 'Content group description' frame is used if the sound belongs to a larger category of sounds/music. For example, classical music is often sorted in different musical sections (e.g. "Piano Concerto","Weather - Hurricane").
This definition is a bit open to interpretation so over the years the frame has been used by different applications in different ways, both as a work and as a way to group multiple tracks in other ways. For example in SongKong it can be used to store genres as a list of values because iTunes Genre can only see the first value, a problem if you want to categorize a song with multiple genres.
In fact until version iTunes 12.5.3 iTunes have always used this frame for the Grouping field. When you update to the version of iTunes your existing files will appear unchanged, but any grouping data that was stored in the TIT1 frame has now silently been moved to iTunes internal database only.
But when you import any new music that had the grouping field set you'll see it no longer shows in the Grouping field of iTunes but the Work field, and this also applies if you update any music outside of iTunes that is already in your iTunes library.
You can see this by going to the Songs view and enabling the Work column, and there are all the missing groups.
I created this test from SongKong very simply by
- Ensuring Update Genres and Save changes to iTunes was enabled on the Basic tab
- Setting Grouping to Always Replace Values on the Genres tab
- and running against a folder of MP3 files
So you can't use the Grouping field anymore, right ?
Well no, once you have added your songs to iTunes you can enter data into the Grouping field and it will persist. But it's no longer actually stored in the TIT1 field itself. Instead it is only added to iTunes internal database. But the problem with this is you can only fill in the Grouping field manually from within iTunes after the file has been imported in. Then once done to get that Grouping data out you would have to use iTunes AppleScript (OS X) or the COM API on Windows, this makes it very difficult to use your organize your songs consistently in both multiple places, such as using with both iTunes and Sonos.
Now for the really crazy part
MP4 files don't use ID3 for metadata they use atoms instead and the ©grp atom does continue to correctly map to the Grouping field if you import MP4 files.
This is because for MP4 Apple has defined the following new fields:
So there are separate fields for Grouping and Work !
Why didn't they define a separate field for Work for ID3 ?
That is the question, by adding new the new frames MVNM and MVIN frames they are already not strictly adhering to the specification anyway so the argument cannot be they did not want to break the standard
What does this mean for me ?
It means that if you use iTunes that when editing metadata for files outside of iTunes you need to consider different audio formats differently.
If you have a mix of Classical and non-Classical and you use AIFF or MP3 then it may be wise not to use the Grouping field for anything other than Works.
One question that requires more thought is when importing MP4 does it make sense to add tracks with the same Work as part of the same Grouping or not.
We will be adding options to SongKong and Jaikoz to make this as simple as we possibly can
Within iTunes it is probably best to decide on a format and stick to it, transcoding different audio formats to a single format.