Tagging MP3's and music files: Multiple Genres & Artists would be GREAT

I'd really love to start using a media library. I have at least 150Gb of music and it would be nice to say, pick a genre and see what it throws up. Some of it is well-organised, a lot of it is not.

But one thing that really irks me is that there's no way to tag a file with several genres or with several artists. For example, 'Cannonball Adderley and Bill Evans' has to be exactly that, but media library software won't connect together all the 'Cannonball Adderley' music with the stuff he did with Bill Evans.

Equally, being able to web-2.0 style tag genres would make life a lot easier for those hard-to-categorise records (like Pete & Fiete: are they flamenco, rock, jazz, what?)

Kevin Keegan has this to say:

I know that ID3v2 supports adding multiple genre tags to a file but does any software support this? I have not seen any that does and I don't understand why. Most music belong in multiple sub genres, take Fleetwood Mac for instance, it belongs in Rock, but also a sub category of Classic Rock. Most people just classify it as Classic Rock, but what if you want to here a mix of all Rock songs, then you would have to select each subgenre of Rock. Also imagine the issue of a song that people can not agree on what the subgenre is.

So first, a strong shout-out to who-ever is coding this stuff, I'd like multiple artist & genre tag-ability! Here's my suggestion:

• It seems to me that the simplest multiple genre implementation would be a tagging style field (in the web-2.0 sense). See del.icio.us or flickr.com for example implementations.
• The user would be free to enter as many genres as they want in free-text, separated by some separator character e.g. ;
• Free-form text input is key for user-friendliness, but to avoid slight derivative spellings forming two genres, tagging software and media libraries could suggest what to write based on the genres already present in the user's library or 'tag cloud'. For example, is it 'electronic', 'electronic music', 'electro', 'electro-pop' or 'electronica'? Or something else? Your media-library would suggest whatever you'd previously used, but you'd equally be free to type electro-punk-funk if you felt like it.
• As long as the ID3 standard doesn't place any limit on the length of the genre field, it is possible to enter multiple genres already. Genre searching features can then be added-on later.

It could be argued that non-standardised genres don't allow interoperability, but taking it a bit further, if genre tags could be listed online somewhere, they would take on a social dimension: i.e. you could utilise not only your genre listings but also those of others. Interoperability could be achieved through the net. Since genres are essentially subjective, this would give a similar consensus opinion, like Wikipedia.

It would also allow cool gadget features like a tag cloud of your MP3 collection.

Thoughts?