Multi-Band Compression in Mastering

Getting back to compression now, a multi-band compressor is essentially three, four, or possibly five compressors in one, with each compressor focusing on a specific band of frequencies. You will almost certainly find all the same controls as on a single-band compressor (that do all the same things), only multiple sets of them. But what really sets it apart is the types of things we use it for.

A multi-band compressor is not as much a tool for giving that layer of gel and bringing a mix to whole as is with the single-band, although it does have some similar benefits. It’s more of a corrective tool for controlling elements within the mix that need some attention. A common use for a multi-band compressor is to tighten up the lower frequencies, such as a bass-line or kick drum. Other uses might be to control a stray loud percussive hit in the high mid. De-essing is a common use too, even in mastering. Another use might be to tighten an under-compressed vocal in the mids. Essentially, a multi-band compressor is a means to tap into the mix and tighten up, tidy up, or whatever is needed.

As the multi-band compressor can be set differently from one frequency band to another, a certain amount of spectral adjustment can be made too. As well as compressing, you can use multi-band for similar reasons as your EQ, such as to balance a particular area of the spectrum.

The only major difference in what you can dial in, compared to single-band, is the adjustment of the affected frequency bands – by that I mean where one compressor ends and the next one begins. With that in mind, it’s quite astonishing just how different the two instruments are.

As with single-band compressors, there’s likely to be a few extra options on your multi-band other than the ones we have already discussed, but they don’t concern us right now. We’re just going to examine the same parameters as we have with the single-band.

image of a multi-band compressor being used in audio mastering

A major difference you will notice when using multi-band compared to single-band is how you set your attack and release times. Because we’re tapping into the mix, it makes sense that the attack and release times are going to be closer to that found with the compressing of single channels, such as vocals or bass for example. The ratio may also be quite different with a resemblance closer to that of channel compression. In general, attack and release times may be shorter and ratios may be higher.

Next page… Multi-Band Compression Situations