[TeamAyu2004]

Originally Posted by Delirium-Zer0

*eyeroll*

"Covers" are by other people.
"Self-covers" (this is a common term used in j-pop by the way, "self-cover" albums are marketed as "self-cover" albums) are covers by the same person. (Hence the "self-" prefix. I don't even see how there's debate about this.)

A remix has only the instrumentation changed. A self-cover has the vocals changed, and usually the instrumentation changed also. A self-cover makes changes as though the artist, in their current form, is a different artist with different talents and artistic ideas and tastes. Which is kind of the truth. A self cover is usually useless if it's done only a year or so after the song originally came out because there's probably not gonna be much difference.

Here's a handy comparison chart:
A Song for XX "she shell REPRODUCTION" (remix) | A Song for XX "030213 Session #2" (self-cover)
Dearest "Depth nostalgic windmix" (remix) | Dearest "Acoustic Piano Version" (self-cover)
Endless sorrow "Natural Green dub mix" (remix) | Endless sorrow ~gone with the wind ver.~ (self-cover)
LOVE~Destiny~ "TODD'S LOVERS CONVERSION" (remix) | LOVE~Destiny~ (10th Anniversary Version) (self-cover)

I hope this makes it easy for everyone to understand so they can stop debating just for the sake of debating.

we could have done without the eye roll.
Yet again, another example of different opinions. everything you mentioned as self covers for ayumi are remixes in my book. The titles say it all... most of them are different versions, that to me has nothing to do with the original, which makes it a remix.
Anything that is different from the original is a remix, i guess call it what it want, its still the same person doing a different version of their song, which in the end is a remix.

also, i would like to point out this nice little article about remixes on wiki:

A remix is a song that has been edited to sound different from the original version. The person who remixed it might have changed the pitch of the singers' voice, changed the tempo and speed and has made the song shorter or longer, or instead of hearing just one person singing they might have duplicated the voice to make it sound like two people are singing, or make the voice echo.

and

Remixes should not be confused with edits, which usually involve shortening a final stereo master for marketing or broadcasting purposes. Another distinction should be made between a remix and a cover. A remix song recombines audio pieces from a recording to create an altered version of the song. A cover is a recording of a song that was previously recorded by someone else.