So, the ALBUM ARTIST tag is for VA albums.

Why is there no tag for specifying if a song belongs to a group, complete album vs. downloaded single?

This is something that is asked about quite frequently.
How should we (do you) show disparity between albums and singles?

I was thinking about using the EXTRAINFO or OWNER tag, but this is wanting.

Using the directory structure is archaic and slow.
Searching next/previous ALBUM/ARTIST is inefficient and I don’t even know if Foobar can do it (I am sure it can).

There needs to be a tag similar to COMPILATION a switch (who uses this?), or ALBUM ARTIST if felt more info need be asserted.

Is there a tag that is missing/needed or am I wasting my time asking?

i use singletrack=1 which is supported with a lot of fcs but maybe there is better solution

I use %type% tag, which has the following values, depending on the release type: album, single, EP.
If the track is a single track (not belonging to an album, single or ep) then it does not have the %type% tag.
BTW, this tag eliminated the need for a single track recognizing script in my ColumnsUI config.

I use singletrack=1 for singles

Wouldn't it work to filter for album gain ? If a track only has track gain, but no album gain then it should be a single track. Only problem is, that you can't really distinguish between a VA album then. On the other hand, I personally have no reason to do that anyway.

I don't use any file tags for this, but comments in the playlist names (like [VA]) to distinguish between album and single track playlists and thus between the "viewing modes".

That way, I can't have mixed playlist, but tracks can be viewed in both ways depending on the playlist they're in.

I was thinking something like…

If a person has several Albums and few Singles, a person could tag their Singles.
If a person has several Singles and few Albums, a person could tag their Albums.

Similar to lofts comment about the TYPE tag.
Or.
SINGLETRACK=1
ALBUMTRACK=1
Or.
TRACKTYPE= 1/single 2/album

What ever the solution…

Do you think there should be a recommended standard?

Personally I remove the track number from all my "single" songs and use this to determine if a song belongs to a full album or not (Do I really care what the track number is if I dont have the whole album? No, maybe you do I dunno). As you can see from the other replies, this has been a long term problem with managing large music collections and many people have come up with many solutions. I would like to see someone come up with some sort of standard that will work for most people but keep in mind that as long as you are relying on tag fields to figure this sort of thing out, it will break as soon as person A downloads a single song from person B over a P2P network instead of the entire album. Of course if you are only managing your own personal collection and not doing any P2P that wouldnt be a problem.

I use directory structure to tell if I have full album of just single track.
I put albums in Artist Name\Album Name and single tracks in Artist Name\~other.

Some time ago I used to use Yotsuya's way (removing track number), but then I became obsessed about correct tagging and I thought that it's a waste to remove track number just for display purposes.

If anyone's interested, a code that check for no track number and "~other" directory is: