The tagnavi syntax is detailed fairly extensively in the
Database Rockbox wiki entry and there are some fairly detailed examples given.
Might I suggest an alternative or secondary option, however?
It would seem to me that this could be solved entirely without using the Database at all if you were to simply have a sane album file tree structure, ie.
/Music
- ./Artist
-- ./../Album
--- ./../../Disc 1|2|...|
---- ./../../../<tracks>
etc.
Note: I really mean 'Album Artist' above when I say 'Artist' as it is my sincere belief that almost no one actually wants to use the artist metadata tag and instead almost always want it to be the album artist tag, to avoid albums being split up weirdly due to contributing artists, ie.
"Artist - Johnny Jonson ft. Billy, Bobby, Betty, Janey, Jack, Timmy, Tom, and Nice Old Mrs. Merthens From Down The Street"
I very strongly believe that almost no one actually wants the artist metadata tag to reflect the artist and contributing artists, but instead want the artist tag to reflect the primary/album artist.
Personally, I think that everyone should have a similar directory structure for their media anyway...and this can be used alongside the Database even if you were to alter your metadata or the tagnavi structure to suit your liking (since the Database doesn't care in the slightest where your media actually is). If you were to do this, and found it suitable for your use case, you could stop using the Database completely if you wished (I honestly do not know a single developer who uses the database functionality outside of testing) and release a non-trivial amount of RAM back to the system for use in the audio buffer.
One other bonus is that having a directory structure like this "Just Works" everywhere.
The only immediately obvious reason to use the database (in my mind) is the rating system, and even that is questionable since the ratings are stored in the database alone and not a part of the metadata (we never alter metadata) and even if the ratings are exported there is no media player I am aware of that recognizes, makes use of, or can convert our rating system so their benefit is questionable.
[Saint]