Tame That Frequency: A Band-Sensitive Compressor

You can also use a sidechain to tune a compressor so that it’s most effective around certain frequencies. This is essentially the concept behind a de-esser. To use a compressor in this way, feed a heavily EQ’d version of the track in question into your compressor’s sidechain input.

For instance, if you had a bass with one particularly out-of-control note, or a singer whose voice sounds overwhelming in a certain range, you could use an EQ to emphasize those frequencies, and then send that signal into the sidechain input. Conversely, if the low frequency content of a signal is causing a compressor to go haywire, a sidechain EQ can ensure that it only reacts to mid-frequency content.

Fortunately, many modern-style plugin compressors, like Pro Tools’ Dynamics III have a sidechain EQ feature like this built right in, and need no extra routing to achieve this effect. But if you want to use a vintage-style plugin or piece of hardware, getting up and running is not difficult at all.

If you think it through, you’ll come to realize that this kind of band-sensitive approach lies at the root of any multiband compressor. In fact, using sidechains and duplicate channels, you could feasibly create a multiband processor out of just about any plugin compressor you own.