Composer list in library browser

[TheOldPresbyope]

Are there just multiple tags named "Genre" in the file?

I'm not sure how technically it is written in the file.

Foobar shows one Genre field with multiple values:
     Classical; Choral

Mp3tag shows it in two way:
  - as two genre fields
  - or as one field separated by double backslashes:
        Classical\\Choral 

The last option (backslashes) are the option I'm using by editing tags with Mp3tag editor.

In the sample collection there are some files with multiple genres, e.g.:
- Butt, John & Dunedin Consort - [2014] Wolfgang Amadeus Mozart- Requiem
- Arte dei Suonatori & Dan Laurin - [2006] The Four Seasons
- Gardner, Edward & BBC Symphony Orchestra - [2013] Witold Lutoslawski- Orchestral Works Vol. 4

Here's an example of the craziness involved. Remember yesterday I used metaflac to add two genre comment lines to my test file (a sampler found on the Internet)? The result is  (output from metaflac --list test.flac):

Code:

METADATA block #1
 type: 4 (VORBIS_COMMENT)
 is last: false
 length: 12426
 vendor string: reference libFLAC 1.2.1 20070917
 comments: 18
   comment[0]: TITLE=Schubert: String Quartet No 14 in D minor 'Death and the Maiden', D810 - Movement 3: Scherzo. Allegro molto
   comment[1]: ARTIST=Takács Quartet
   comment[2]: ALBUM=Schubert: Death & the Maiden
   comment[3]: UPC=0034571175850
   comment[4]: TRACKNUMBER=3
   comment[5]: TOTALTRACKS=8
   comment[6]: DISCNUMBER=1
   comment[7]: TOTALDISCS=1
   comment[8]: ALBUMARTIST=Takács Quartet
   comment[9]: COMPOSER=Schubert, Franz (1797-1828)
   comment[10]: COPYRIGHT=© Hyperion Records Ltd, London
   comment[11]: DISCTOTAL=1
   comment[12]: TRACKTOTAL=8
   comment[13]: DATE=2006
   comment[14]: GENRE=Classical
   comment[15]: LYRICS=Album notes:
<<<...deleted a long musicological commentary on this quartet...>>>
   comment[16]: GENRE=Chamber
   comment[17]: GENRE=Quartet

 
This file results in three separate line-items in the Genres column of the moOde Library panel.

When I open this file with EasyTAG, a single Genre line is displayed: "Classical - Chamber - Quartet".

When I open this file with Mp3tag, a single Genre line is displayed: "Classical\\Chamber\\Quartet".

When this file is discovered by MusicBranz Picard, a single Genre line is displayed: "Classical; Chamber; Quartet".

In Mp3tag, I edited the tag to "Classical\\Chamber" and saved the file. Examining it again with metaflac reveals that Mp3tag deleted the Vorbis comment line "GENRE=Quartet". (It also renumbered the comment lines and also did some things like change "ARTIST" to "Artist" (same with "ALBUM", "GENRE", "TITLE"; perhaps because I didn't change default settings?)

I then used EasyTAG to re-edit the tag to "Classical - Chamber - Quartet" and saved the file. Now metaflac displays a single comment line "GENRE=Classical - Chamber - Quartet". (Also, EasyTAG reverted the labels Mp3tag had changed back to all caps and deleted the LYRICS comment!). This would, of course, show up as a single compound line-item in the moOde Library panel.

I then used Mp3tag to re-edit the tag from "Classical - Chamber - Quartet" to "Classical\\Chamber\\Quartet" and saved the file. Now metaflac again reports three GENRE comment lines.
 
Once the file is discovered in MusicBRANZ Picard and I choose to edit its genre line, a box opens which offers each genre tag as a separate value and lets me edit, add or delete values. Each value is written to the file as a separate Vorbis comment line. It also reverts tag labels to all-caps.

Lesson learned: trust but verify your tools; they may be doing unexpected things.

I don't know how multiple genres are handled in other file formats but if I get a chance I'll try a few test cases. I'll have to see what other Linux-friendly tools I can try as well.

My personal preference is for multiple genre lines in a file rather than an single, compound one.

Regards 
Kent