Because I was unable to receive an official confirmation from the possible original creators I decided to try my luck here :-)

I put this post on the Musepack and Monkey's Audio forum as well as contacting Frank Klemm directly but no response or not all problems got solved.

To clear things up a bit first: where did the APE tag system originated from? I'm a bit confused and not a 100% sure because the name would imply that it originated from the Monkey's Audio format, though this site doesn't realy contain any info about it.
I only found some complete info on APEv2 on Frank Klemm's site so that would imply that Musepack created the APE format [1]. Please forgive me for my ignorance, I might be completely off here. :-)

I'm currently working on a tag frame reference of the different tag sets (ID3, APE, Vorbis, Matroska, etc.) and because of that I've got several questions about the defined APE tag keys [2].

I'm having trouble creating an accurate mapping of the following tags because the exact definition isn't exactly clear to me.

- FILE
Does the location of the file need to be stored in the tags of the
same file? What's the point? What exact type of location are we talking about since it
has to be a URL?
- MEDIA
I don't get this one, what is it that you want to have stored in this
tag? Is it like the WWWAUDIOSOURCE (WOAS) frame in ID3 [3]? WOAS is
used to point to the official webpage for the source of the audio
file; e.g. if the audio is "extracted" from a movie. This doesn't
explain the Source Media Number/Total Media Number and Source Time
though.
It has also been suggested that it's used for Though this wouldn't explain the Source Time needed as well.
- INDEX
Indexes for quick access? Quick access of what? Can this key be
compared to the MPEGLOOKUP (MLLT) frame in ID3 [4]? This one is used
for a MPEG location lookup table to increase performance and accuracy
of jumps within an audio file. Or am I completely off here? Smile

And just in case:
- RELATED
Location to what kind of related info? Just any kind of info related to the file?
- ABSTRACT
Abstract as in a description or summary of the content? If so, why does it need
to be a link? Because of the tag key size limit?

Thank you in advance for your time and help.

Cheers,

Prodoc


[1] http://www.personal.uni-jena.de/~pfk/mpp/sv8/apekey.html
[2] http://hobba.hobba.nl/audio/tag_frame_reference.html
[3] http://www.unixgods.org/~tilo/ID3/docs/id3...rames.html#WOAS
[4] http://www.unixgods.org/~tilo/ID3/docs/id3...rames.html#MLLT

I've tried to give an answer here. Maybe someone can give some additional feedback.

Best regards,
~ Florian

The problem is that no one so far seems to be able to realy confirm anything. That's why I desided to post it here as well because it might reach a larger amount of users.

I think ganymed is right that APEv1 was used by Monkey's Audio and APEv2 by MPC (the differences aren't huge btw), Monkey's Audio now uses APEv2 too.Like ganymed I also haven't seen this used before, but maybe it was meant to be used with streaming?I'd say it can be used for either:

• Media type
  
• Index/Total for use with albums spanning multiple discs.
  
• Source Time might be for use with things like tapes, but I don't know.

Perhaps it's meant to be like a bookmark.

There is also an overview of mappings between different tag formats somewhere on HA, you should probably be able to find it with a bit of searching (I think it was mentioned in relation with Matroska tags, so you may have luck by searching for that).

That's the one I'm working on

Tag Frame Reference