Here's my take on why CD keep sounding louder and louder.  And this 
has been going on since the 60's, when The Who claimed to have to loudest 
record (don't recall which), but they cranked it up as much as possible 
before the needle would skip into the next groove on the cutting lathe.  
(That's I believe what Paul McCartney read about that influenced him later to 
write Helter Skelter).  And of course the Beatles followed suit with 
Paperback Writer, this first time, I believe, that anybody stuck a mic inside 
a bass drum for a studio recording.  that was mastered using the now famous 
Abbey Road mastering compressors (now re-released and known as the "Hey Jude" 
compressor).  It's simple really, just crank up the volume and increase the 
track pitch on the lathe.  The goal for the last 35 years has been (in pop 
styles anyway, not classical), to make ever-louder records and CD's.  When 
the first CD's came out, they didn't even take advantage of the full 16-bits 
of the medium.  The Elvis #1 Hits double disc package are mastered at 6dB 
down from peak!  talk about weak.  That's equivalent to a 15-bit recording!!  
Yuck.
    Then, once they figured out the CD medium, they discovered NORMALIZATION, 
where they would never have to release a CD again that didn't use every last 
bit on the CD - volume-maximized to take advantage of that full 2-volt swing, 
baby.
       THEN, they had to go back and "digitally remaster" everything to crank 
up the volume to "today's hip-hop and pop standards".  That means they 
discovered newer digital compressors that could compress the shit out of a 
track.  That means it smashes down those annoying peaks that rob you of 
headroom on the CD, allowing you to increase the overall volume.  DX plugins 
such as WaveHammer, and Waves compressors became the rage of the last few 
years.  Just rip any modern disc into a wave-editor and they look like a 
brick instead of an envelope of changing volume.
       One reason they do this is to sound louder and "better" over the 
radiowaves.  The human ear is almost always duped into "louder sounds better" 
(Those doubting should check out the famous paper by Fletcher and Munson, 
available I'm sure somewhere on the web)  This is why you should do ALL 
comparisons of speakers, mics, and mixes AT THE SAME VOLUME LEVEL.  ALWAYS.  
Or your decisions will be biased.  Your ears are not flat, and in fact 
fluctuate in response to changing volume levels.
       I am not a fan of the latest wave of over-compressed CD re-releases.  
For one, it smashes down those nice peaks to be level with everything else, 
then it brings up those soft subtle sounds like a nice guitar picking, finger 
slips etc. to an almost annoying level.  If you compare ELO's remastered CD's 
to the older late 80-'s releases, and George Harrison's re-release of All 
Things Must Pass to the older one, AT THE SAME VOLUME, I think more often 
than not, you would pick the older normalized stuff to the newer smashed 
stuff.  It just sounds more natural, dammit!
       Try it, and let me know what you think.  I'd love to get feedback from 
you folks.  In fact, I've had those above cd's sitting on my computer, where 
I've been meaning to volume-equalise the two and print them to disc for 
comparison.  If I get enuff interest, I may post those somewhere for download.
       Well, this post is long enuff - see my next post re: rereleases of 
rare gems.
-Mike 'wiz' Wisland