Monday, May 25, 2009

A dispatch from the loudness wars -- compression and the future of music

With much ‘gentle persuasion’ (arm twisting), I’ve managed to convince an audiophile mate, Michael, to write some words on a development that disturbs many people with a strong interest in sound quality – the increasing use of compression in commercially produced music. Below, Michael explains what compression is and why it’s bad for listeners and the music industry.

When music is played there is great variation in the loudness of different sounds. Lots of recorded music now compresses the recording so that the loudest bits become quieter. This enables engineers to turn up the overall sound. As a result, the recording as a whole is louder but with little variation in sound levels.

If you compare a CD made in the 1980s with a recent CD, you’ll probably find that the old CD sounds very quiet compared with the recent one. (It makes an even better demonstration if you have a recently remastered version and can compare the two versions of the same track.)

It is when you turn the old CD up so that it sounds as loud as the new CD that you really hear the effects of compression. The old CD will sound alive and like ‘real music’. This is because it reproduces all the natural peaks of real music. Drums sound like real drums.

The new CD doesn’t sound like real music. Even on a really good system it sounds as if you’re listening to a radio program.

Because a compressed track sounds louder than an uncompressed track, and more and more compression is being used as each recording strives to be just a bit louder than other recordings, the overuse of compression is known as ‘the loudness wars’.

There is a clip on YouTube which demonstrates the problem. (Note that unless you have very good computer speakers you might not hear much difference in this short clip. Also note that it is now common to use much more compression than is demonstrated on this clip.)

A little compression goes a long way
Some compression has always been used when recording, mixing and mastering music. This is fine when carried out appropriately in small doses, like a chef who uses a pinch of salt.

What is done now to music is like the waiter sprinkling a tablespoon of salt over each meal on the way to the table.

In the ‘olden days’ it was more common to spend time sitting down and actually listening to music rather than doing other things while music played in the background.

When all the natural peaks of the music are cut off by compression the sound is very different. At first the ear often thinks the music sounds good – compression can make some parts of the music sound clearer. But after 20 or so minutes the ear rebels against this unnatural and distorted sound. Not only do you want to turn the music down, but you lose interest in it and want to do something else.

Just as a meal with too much salt might be tasty at first but become inedible after a number of bites, today’s compressed music can be unlistenable if you try to sit down and listen to a whole album at a reasonable volume. In contrast, listening to loud music for a long time is enjoyable when it has not been overly compressed.

The music on most DVDs has a much more natural dynamic and much less compression than modern CDs. This is why you can still enjoy the audio of a DVD even towards the end. If you’ve ever wondered why music in the cinema or on a DVD sounds better and more lifelike than the CD, now you know that it’s all due to the movie version having less compression.

The compression of the dynamics of the music – discussed above – is totally different from the compression carried out for MP3 purposes. A low bit-rate MP3 file does lose some of the musical detail (which is why MP3s sound better if a higher bit rate is used), but making an MP3 file from a CD does not affect the dynamics.

Related developments
Some music is now released on vinyl as an audiophile option. Some audiophiles think that vinyl sounds better than CD and are prepared to pay extra for it. Even though a CD can record a greater dynamic range than vinyl, it is now common for the vinyl version to be less compressed than the CD. Irrespective of the debate between vinyl and CD, the less compressed vinyl really will sound better.

One irony is that as compression becomes more and more popular with mixers (who assume, I suppose, that their listeners want it), so musicians themselves seem to be agreeing to it, thinking it sounds good. Also ironic is the fact that all this is happening at a time when the ability to effectively transmute all the variations and permutations of sounds through high quality digital means has never been greater.

But there is worse. When you buy a remastered CD that has been heavily compressed the original master tape will remain uncompressed. This tape can be used again one day to re-release an uncompressed CD. But as compression has become the ‘industry standard’ it is becoming common to record and mix compressed music. If the master tapes are compressed then this music is compressed for all time.

If you’re interested in finding out more about this issue or would like to join the discussion, check out Turn Me Up, a site devoted to the fight against excessive compression. This site includes lots of links to references and news articles, and is a great place to find out more.

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