[Playlist] Music tagging

[M@d Man]

Hello!
>> The instrument tag would look like this 
>> "http://example.com/meta/audio/0.1/artist/instrument/guitar" and if 
>> there is more than one player of a certain instrument you can add a 
>> number to the end (i.e ".../artist/intrument/guitar/2/sort_name" for the 
>> sort key of the second guitar player).
>>     
>
> Can you explain this in more detail please?
>   
My original intention was to introduce a possibility to name the artists 
who play the instruments. In classical music there are often soloists or 
if we look at popular music we could name every band member. But there 
shouldn't be a restrictive list which instruments can be used, so the 
instruments ave variable (indicated by the <> brackets). So I thought 
about a scheme like ../artist/instrument/guitar.
But as there could be more the one guitarist in a band I couldn't use 
the "sort name" unambiguous anymore. If there are for example two 
guitarists with the "../artist/instrument/guitar" tag, let's say "John 
Lennon" and "George Harrison", and the corrisponding sort names, say 
"Lennon, John" and "Harrison, George", wich sort name belongs to which 
artist name? My solution was, if there are sort names involved, I have 
to number the artists (so ../guitar/1/ for John and ../guitar/2/ for 
George).
Same with the role tag. The "../artist/role" tag is proposed for people 
involved in the music but didn't made the music themselves (i.e. a 
producer tag looks like this "../artist/role/producer").

>
> I like the idea, I think official XSPF extensions are a good thing.
>
> I have two questions at the moment:
>
>  - For a two-disc album I assume <album.total_tracks> holds
>    the sum of the number of tracks on the first and the second disc.
>    How do we specify the number of tracks for each disc?
>   
I didn't think about that, but you are right, there should be an 
indication for this. There could be also a "../disc/total_tracks/" tag.
>  - Some of these are already handled by XSPF, e.g. <track.title>
>    I assume we omit these on meta and that you added them for completeness?
>   
Yes and no. For XSPF I would leave them out. But as you said for 
completeness they should be in a kind of specification. This proposal 
could be also used by rss feeds or other services where you have to 
identify meta data (like MusicBrainz, last.fm or similar).

I forgot to mention the ability of this scheme to adress different 
levels of complexity for the tags. Namely if you don't want to use the 
instrument or composer parts of the artist tag you could identify the 
main artist simply by ../artist/ and if you don't know the specific 
dates you can use ../date/ instead. This however doesn't work for all 
nodes in the hierarchy. Again these tags are already handled by XSPF 
natively, but for a complete tag description they are essential.

Clemens