Why would you want to assign multiple genres to an album or piece of music? I think there are two main reasons. The first is, if you have adopted a very specific genre categorisation, there may be multiple sub genres that you think apply to some music. For instance, you may label Loveless by My Bloody Valentine as both 'Shoegaze' and 'Alternative'. Another reason is if you want to maintain both a specific and general genre list. In this example, you may also assign the 'Rock' genre to Loveless. This way the album appears when either the Rock, Shoegaze or Alternative genres are browsed.
So, in some cases, it feels unnatural to just pick one genre
The genre for your digital music is stored in the music file's tags. A tag with the title 'genre' stores the genre value. This is either plain text, for instance 'Rock', or in the case of an ID3 tag (used in MP3 files) it may be a number. By changing this tag, you can change the genre. But how do we add genres?
The trouble is, multiple genres are not widely supported by music players. And those that do sometimes require your genre tags to be specially composed, with special characters separating the genres. Once you've worked out that your player supports multiple genres, you can start adding them. If you're really lucky, your music player itself may offer support for adding genres, but otherwise you will have to use a music tagger to edit your genre tags. The tagger may take care of how the tags are written for you, but in case it doesn't, here's how you should edit your tags to add a genre:
WMA, OGG and FLAC. These file formats explicitly support multiple genre tags. You should simply add a new genre tag with your additional genre. If your music tagger supports multiple genres, it should simply add a new genre tag for you. When you refresh your music player, assuming it supports multiple genres, you should now see your music categorised under both genres.
MP3. MP3s (or rather, the ID3 tagging format used by MP3s) don't support multiple tags for genre. Instead you must use the one existing tag and use a delimiter character to separate the genres within that tag. If your music tagger supports multiple genres, it will add the genres separated by the delimiter for you. If it doesn't you can always do it manually by manually adding the delimiter.
What delimiter should be used? The de facto standard most music players adopt is to use the semi-colon character. For instance, your genre tag should appear as so:
GENRE = Rock;Shoegazing;Alternative
Alternatives are suggested in the ID3v2.4 specifications. The former suggests forward slashes '/' although this stands a good chance of clashing with genre names with slashes in them! The latter suggests 'null' separators that may be hard to type. I suggest going with semi-colons.
An alternative is to use a specific tag that you know is supported by your music player. The tag depends on your file format, but possible tags to try in MP3s specifically are:
Again, you may be able to use delimiters in these tags if you feel it appropriate. Furthermore, for iTunes AAC files, try the @grp tag.
I hope these hints have provided some ways in which you can add genres to your digital music files!
Thanks to mandiberg for the image above.