Talk to everyone from armchair music production critics to dyed-in-the-wool pro engineers, and you’re likely to hear about how today’s records are over-compressed. (We think this is what Bob Dylan meant when he said records “have sound all over them.” But we made fun of him anyway.)

To audio lay people, though, it may be tough to describe exactly what this means. One music fan has taken the battle to YouTube, with a graphical and aural demonstration of exactly what the technique (technically “brick wall limiting”) does to the sound. Rather than approach this the traditional way, he takes a nice, clean 80s track and imagines what it might sound like in 2007. It’s actually not an implausible result:

(thanks to Matrix of Matrixsynth fame)

More experienced engineers have pointed this out, and can even demonstrate visually using actual examples, but this does as good a job as any explaining what happens — in particular, when you re-adjust dynamic levels for different equipment. A common misconception is that compressing audio levels makes it sound better on cheaper equipment and at more listening levels. That can be true to a point, but squash dynamic range, and poorer equipment can actually make things sound worse.

This said, I’ve noticed some important points often get left out of this discussion:

1. Brick wall limiting should not be blamed on digital recording — or visa versa. The whole idea of pumping up tracks’ loudness to boost record sales is largely a result of FM radio as the mechanism for promoting tracks.

2. Not every track you hear in 2007 uses heavy compression. On the contrary, there are some beautifully-produced albums out there, and with the explosion of indie labels, a lot of albums are aimed at aficionados with headphones, not mass-market loudness.

3. Over-compression isn’t always bad. It’s a stylistic hallmark of a lot of modern hip-hop — which in turn might be thought of as a nod to dub and other traditions. It just tends to get applied without artistic intent in some albums.

With the growth in home recording, in fact, this example doesn’t have to just be a criticism of the record industry — it can also be a cautionary tale for being careful with how you use compression. Dynamic range is just as important an area as frequency range, and any reminder of that is worth considering. So before we start whining about other people’s recordings, it’s worth thinking about what different dynamic ranges do to our own music.

For more information: There’s a very knowledgeable rant on this topic in engineer Bob Katz’s book, Mastering Audio: The Art and the Science, which is an unparalleled reference on mastering in general. (And it’s worth separating the art of mastering from what a lot of us do, which may or may not have a delivery medium in mind. Not to mention, the basic rule of mastering material well is, give it to someone else who knows what they’re doing and touch it yourself as little as possible.) Katz most definitely knows what he’s talking about, and his frustration with this evolution — or devolution — of mastering comes from years of experience. That’s not to say people can’t disagree with him on some of his points, so I’d be curious to know what others think.

Elsewhere: Tom at Music thing linked to a helpful visual aid showing the evils of “Living La Vida Loca” as a new, digital wall of sound. More discussion there.