How does the actual remastering process of a song work?
I mean once a song is glued together with all the parts,
how does someone go back and make any worthy changes to one part
of it without changing the rest?

Beyond the "remastered" versions sounding louder, are there other changes
that go along with "remastered" that I don't understand?

Good question, I always wondered about this also.

So many 80's CD's sound lower than CD's from today.

i bought the "remastered" 3 feet high and rising and its fucking terrible sound-very quiet

yeah i wonder that too!

Ra-mastered means basically taking that original and putting it up to date with current standards.

Making the bass more prominent, making the instruments more clear. Some re-mastered music sounds great. You can hear percussion instruments you didn't even know ere in the song.

A remaster these days involves taking the original stereo mix tape (or the closest master copy available - digital or analog) - transferring it to a digital workstation using a higher resolution and bit rate than was capable during the early years of the CD. Then some careful equalization is applied (when necessary) and also (when necessary) compression and limiting. Some noise filtering or noise reduction is sometimes applied when the tape is very hissy or if there are non-musical noises present on the tape (clicks or pops).
Limiting is used when a song has maybe one or two very high peaks so that the overall volume of the song can be increased.
I do think though that many engineers go overboard with fucking with the original sound, often resulting in CDs that give you ear fatigue after a few minutes, because they are so compressed/maximised or the EQ is either ear-bleedingly bright or way too boomy.
I don't think the purpose of remastering should be JUST to raise the overall volume of the songs and if a remaster sounds "fucking terrible" it's probably not because it's very quiet. Try turning up the volume (stereos still have volume controls, right?) and if stills sounds like crap, the problem could be that they used the wrong source tape, the EQ is messed up or the original recording itself wasn't very well engineered to begin with.
I've noticed that some people here claim that the Prince CDs that were re-released in Japan this year are not remasters. I own a few of those and while the differences are not night-and-day in most cases, it's obvious that some work has been done.
Like I said, remastering involves using a stereo tape, NOT going back to the multitracks as some have suggested. Besides, remixing these songs could ruin the sound Prince intended for those songs. Whether they used the original master tape for those mini-LP releases doesn't make a difference if we're debating whether they are remastered or not.
Judging from what I've heard, especially noticeable in the track "D.M.S.R." on 1999 , after comparing to the older CDs it is clear that Warner Japan transferred whatever tapes they had for the albums to a digital workstation and did some rather conservative adjustments to the sound.
That is considered a remaster, and you would be suprised how many albums that proudly claim they have been remastered go through the exact same process. Record companies can sometimes be lazy and they don't always go for the best sources. You can only be 100% sure you're getting a remaster from the original tapes when you buy CDs from specialist audiophile labels like Mobile Fidelity and Audio Fidelity.
Some might ask, if the CDs are indeed remastered, why doesn't it say so on the packaging?
There are many cases where CDs are remastered without any announcements on the packaging. For example, the first Metallica CDs were remastered in the 90s and the only way you can identify the newer CDs from the outer packaging is the text "E/M Ventures" which is present on the newer CDs. The Ultimate Prince compilation is another example, although some have suggested that it wasn't mentioned in the liner notes for legal reasons.

jonylawson said:

the reason why older cd's sound "quiet" is because today's music is fucking compressed and limited to death, that all the dynamics of the original recordings virtually dissapear.

a good example is metallica's last album. the retail cd's sound was so loud that it was disgustingly over compressed beyond acceptable levels.

thats why the fans went and ripped the audio from the guitar hero game version, as that was the proper version of the audio as it should have been!

music today is super compressed and too loud, and in fact its so loud that some times, individual instruments of songs are no longer clear enough to be heard.

for some reason, these labels have a loudness war, which means they want to crank up the volume for no reason on these recordings.

look it up on youtube. most albums today are fucked, and close to breaking point.

there is a reason why your stereo has a fucking volume button on it. its supposed to be used! but unfortunately kids today are tone deaf.

bunch of morons!

LittleBLUECorvette said:

current standards are shit.

its the reason why so many recordings are now being limited to death.

of course, when remastered correctly, older recordings are improved.
but todays levels are far distorted and actually ruin the original recordings.

dirtyman2005 said:

Nothing has hurt music more than digital. The whole going "digital" may be what people want, no more actuall cds but if you think the transfer loss from vinyl to cd was bad, doing things directly to mp3-4's is the worst of all.

dirtyman2005 said:

i just could not hear ANY difference between 3 feet high n rising and the "remastered"

unlike the other remastered shit ive heard

i agree with your comments though