C is for compression

 

One of the most important elements in music making is one of the most difficult to detect, as it is something we take for granted every time we listen to an album.

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Compression techniques run seamlessly through the background of music production as studio producers tweak knobs to give music aficionados the most even and professional listening quality possible.

However, another form of compression in music is more recognisable due to the popularity of downloading compressed music files from iTunes and Napster when you download an MP3.

The two forms of compression mentioned, are different but as important as each other nowadays – yet, never will the twain meet except in listening to the final product on an iPod.

They don’t sound very good live!?!

Compression conducted in the studio is also known as audio level compression or limiting. It is a process that manipulates the dynamic range of an audio signal, that is, studio engineers use a compressor to tweak the different levels of sound coming from different instruments to bring them together in a smooth and balanced sounding way.

Musical instruments and the players of them are not always playing their music with balanced volume and sometimes have harsh sounding peaks which can result in distortion. What needs to be achieved by the producer, working the compressor equipment, is for the sound to be consistently in, what is called on the meters, the ‘nominal level’.

Once you have set a good recording level for your instrument, which is at or near the nominal level, you will notice that the incoming signal occasionally jumps up into the red. That is usually going to be the nature of the instrument, the musician, or both. The resulting distortions should not go to tape and ruin an otherwise perfect sounding performance. Evening out the imperfections for balanced sound is where the compressor comes in.

Famously, Iggy and the Stooges recorded Raw Power consistently in the red, but that was a definitive rare occurrence.

However, the finished product of a compressed track is not perceived to have changed to an untrained ear. The compressor in the studio can be seen as the great master illusionist as it has the power to make the drums seem soft in places while making heavy metal guitars seem loud, when in reality they are playing at a reasonable and well-behaved volume.

The most common use for compression is when it is used to make music sound louder without increasing its amplitude. (Amplitude, in music recording terms, means the measurement of the height of sound waves recorded; that is, the power of sound coming through the system that is measured in waves on the meter). More often a characteristic of rock and pop music production, a heavily compressed track sounds loud without causing distortion or rattling speakers.

The pedal can also be used to sustain the length of a held note. Imagine Slash with his foot on the pedal feeling that long note like there’s no tomorrow.

When electric guitarists play live they can also compress their sound from the convenience of a pedal and do so in order to control the highs and lows of amplitude. Basically, compression balances out the guitarists sound by limiting the high peaks and boosting the quieter lows to create an overall even volume.

The pedal can also be used to sustain the length of a held note. Imagine Slash with his foot on the pedal feeling that long note like there’s no tomorrow.

How did that big song fit into such a little player?

The other side of the compression coin works much differently. Compression in internet music files works by reducing the size of digital information to make transmitting and download time a quick process, and fit onto small devices such as a portable MP3 player or a mobile phone.

There are two approaches to achieve this and that is via a lossy or lossless compression, and today, there is still much debate over which type sounds better once played.

The jury is still out on what format has the best sound when tests have suggested that some audio codecs such as WMA and RealAudio outplay the MP3 in quality.

Lossless compression works like other digital compression techniques used to compress non-music files found on the PC. The compression program tells the computer’s processor to look for patterns in the file’s code and to create its own much smaller replacement pattern to stand in for the all the originals together at once, hence, the replacement code compresses all similar patterns into one.

Some lossless compressors are Wavpack and Monkey Audio and are great for music as this system keeps the original music file intact.

Lossy compression, however, works on a philosophy that the human ear can only hear so many sounds in a song and discards what it deems to be “wasted space.” Working as a separate codec (a codec is any technology for compressing and decompressing data), lossy compression functions as a separate piece of software that bolts onto an operating system with support for a particular audio playback format.

These very successful lossy compression formats, MPEG, Windows Media Audio (WMA) and Real Audio, and their players are also adapted to play the king of compressed music files, the MP3.

The MP3 is a lossy compression, and although it has a very complex compression process meaning you need a very fast and sturdy computer on which to do the compression, it is still the most successful format as it is said to offer the best quality of playback even at its smallest size.

However, the jury is still out on what format has the best sound when tests have suggested that some audio codecs such as WMA and RealAudio outplay the MP3 in quality, but with the goal for the sound being “CD quality”, the MP3 is sufficient and bands release singles and albums over the internet in the MP3 format today.

The other alternative is to sit on the fence and croon that music has never sounded better than it has on vinyl anyway.

Compression for life.

All in all, brilliant music is more than just great musicianship, but rather, having a good grasp on the concept of compression. As a musician, compression will become an important element to you whether in your recording quality or in releasing music as an MP3 - compression is just a fact of musical life.

For the listeners using an iPod, compression is a fact of daily life, but for music producers, compression is something of an art, and mastering compression techniques will help make all of your recordings sound more professional.

Further reading:

Advanced studio compression techniques.

A kickstart in recording compression.

Lossy vs lossless compression.

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