ROBERT SIEGEL, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel. And today we conclude our look back at the decade that's coming to a close and the dramatic changes we've heard in the music industry with a story about compression, the kind of audio or dynamic compression that's used in a lot of popular music.

There's a YouTube video that uses Paul McCartney's 1989 song "Figure of Eight" as an example. Let's listen. Notice how the drums stand out on the CD as it was released.

(Soundbite of song, "Figure of Eight")

SIEGEL: Now, let's listen to how this song might have sounded if it were recorded more recently, using compressors that squash the music to make it uniformly loud, so it jumps out of your radio or your iPod.

(Soundbite of song, "Figure of Eight")

Mr. BOB LUDWIG (Mastering Engineer): It really no longer sounds like a snare drum with a very sharp attack; it sounds more like somebody patting on a piece of leather or something like that.

SIEGEL: That's Bob Ludwig, a longtime record mastering engineer who directed us to the YouTube video, called "The Loudness War." Like so many conflicts, Bob Ludwig says it has escalated in recent years.

Mr. LUDWIG: The thing that kind of brought everything to a head was this latest Metallica release, the "Death Magnetic" record. It was put on Guitar Hero. It came out to the fans simultaneously both as the Guitar Hero and the final CD. And the Guitar Hero doesn't have all the digital domain compression that the CD had. So the fans were able to hear what it could have been before this compression.

(Soundbite of music)

Mr. LUDWIG: Apparently, 10,000 or more fans signed a petition online to get them to remix the record. That record is so loud, there is an outfit in Europe called ITU that now has standardization measurements for long-term loudness and that Metallica record is one of the loudest records ever produced.

(Soundbite of music)

Mr. LUDWIG: You know, people talk about downloads hurting record sales. I and some other people would submit that another thing that's hurting record sales these days is the fact that they are so compressed that the ear just gets tired of it.

SIEGEL: I'm thinking back to a long time ago, when I remember working at a Top 40 radio station, and somebody put on a 45 and showed me, look at the VU meter right now, and here's a piece of music - maybe it was, you know, some Phil Spector production.

(Soundbite of song, "Da Do Ron Ron")

THE CRYSTALS (Music Group): (Singing) I met him on a Monday, and my heart stood still, da do ron ron ron, da do ron ron.

SIEGEL: The needle is barely moving during it.

Mr. LUDWIG: Yes, indeed. I mean, certainly the loudness wars have gone back to the days of 45s, when I first got into the business, and what is doing a lot of disk-cutting, one producer after another just wanted to have his 45 sound louder than the next guy's so that when the program director at the Top 40 radio station was going through his stack of 45s to decide which two or three he was going to add that week that the record would kind of jump out to the program director, orally at least.

SIEGEL: Now Bob, we're operating at a paradoxical disadvantage here because by the time music comes from us here at NPR to our station, it's compressed.

Mr. LUDWIG: Absolutely. The good news is that the compression that's on those radio station limiters is not quite as bad as you'd find on your local Top 40 radio station. It's not like the FCC allows them to broadcast with a bigger signal than the NPR stations, it's just that they're more highly compressed, and the ear thinks that it's louder.

SIEGEL: Now, I want you to tell me about this recording by Guns N' Roses.

Mr. LUDWIG: Oh, this was great. Axel Rose had had this record called "Chinese Democracy," and he's had it mastered at a few other places, and everybody was doing the normal make-it-louder, make-it-louder thing, and Axel really wanted it to have the final CD represent what he had mixed, which in this case is many layers of guitars. There's a lot going on in this record, many, many tracks.

(Soundbite of song, "Chinese Democracy")

Mr. LUDWIG: Lo and behold, when it gets loud, it actually does get louder, and when it gets soft, it gets softer.

SIEGEL: So your bottom-line verdict from your standpoint on the decade in recorded music?

Mr. LUDWIG: It's been really rough, folks, but it can get better, and I think it will get better. So I'm glad it's going to be over.

SIEGEL: Bob Ludwig, thank you very much for talking with us.

Mr. LUDWIG: Thank you.

SIEGEL: Bob Ludwig is a mastering engineer who's been working in music recording for more than 40 years. Today, he runs Gateway Mastering Studios in Portland, Maine.

Ludwig was talking about dynamic compression, taking the sound of music and making the quiet parts louder and the loud parts a little quieter so that you're not fiddling with the volume knob while you're driving.

Well, there is another kind of compression going on today, one that allows us to carry hundreds of songs in our iPods, and there's a cost to this kind of compression, as well. It seems that some sounds are obliterated in the process.

Joining us to talk about what we hear and how we hear it is Dr. Andrew Oxenham. He's an associate professor in the psychology department at the University of Minnesota, and his specialty is auditory perception, how our brains and ears interact. He also started out as a recording engineer, by the way. Professor Oxenham, welcome.

Dr. ANDREW OXENHAM (Associate Professor, Psychology Department, University of Minnesota): Thank you, pleasure to be here.

SIEGEL: And I'd like you first to just explain digital compression, the process that allows a song to go from being a very big digital sound file in its natural state to a very small file in your iPod.

Dr. OXENHAM: That's right, and that's really the challenge is to maintain the quality of CD, but to stuff it into a much smaller space. Let's think about how digital recording works. You start off with a very smooth sound wave, and we're trying to store that in digital form. So we're really trying to reproduce a smooth curve in terms of these square blocks, which are the digital numbers.

And the difference between the smooth curve and the sharp edges that you end up with in the digital recording you can think of as noise because that is perceived as noise. It's perceived as an error, something that wasn't there in the original recording.

The trick is to take the noise, which is the (unintelligible), and just make it so that you can't hear it anymore.

SIEGEL: So let's say I'm listening to Brahms on my MP3, and it's a loud part of the symphony, are they cheating a little bit here and actually pulling away lots of bits of that sound, knowing that my ears are going to hear loud orchestra, and I'll process it as loud orchestra no matter what's in there?

Dr. OXENHAM: That's right. You can think of it that way. The loud sound is giving the coding system a lot of leeway to code things not quite as accurately as it would have to because the ear is being stimulated so much by the loud sound, it won't pick up very small very small variations produced by the coding errors.

SIEGEL: It sounds like the audio equivalent of a mortgage-backed security, lots of - you know, they've done a lot of tricky stuff in there in the middle, but the end result looks pretty good, sounds pretty good.

Dr. OXENHAM: That's right. It's the sausage factory. You just don't want to know what goes into it.

SIEGEL: Well, in the end, are we missing something when we listen to music that is digitized in this fashion, when it's compressed, or since we can't hear the difference, is it just as good?

Dr. OXENHAM: There are really different levels of MP3 coding. You can go from much less data, which people can hear the difference, to higher levels of coding, which take up more space on your MP3 player but sound better and are basically indistinguishable from the CD, and I would argue that under proper listening conditions, if it's really indistinguishable from the CD, as far as your ear is concerned, then you really haven't lost anything perceptually.

SIEGEL: Well, Andrew Oxenham, thank you very much for talking with us today.

Dr. OXENHAM: Thank you very much. It's been a pleasure.

SIEGEL: Andrew Oxenham is associate professor of psychology at the University of Minnesota, where he also works with the Auditory Perception and Cognition Lab. For more examples of compression, you can visit our Web site, nprmusic.org.

(Soundbite of music)

SIEGEL: You are listening to ALL THINGS CONSIDERED from NPR News.

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