When precision is needed in the audio world, many engineers make use of multiband processing. Like mid to side processors, which break a mix into separate parts so they can be individually manipulated, multiband tools are able to separate the frequency bands of a mix for similar purposes. Think of them as equalizers that allow processing on the individual filtered sections. Typically, only three or four bands are used in these tools. This is because some heavy duty processing is provided for each band in parallel. That means, they’re actually like using three or more processors at the same time. The weapon of choice, today, is a compressor. Others out there, include limiting, exciting, or even saturation.
The idea behind multiband is that a specific frequency range can be given what it needs without applying it to the whole mix. It’s a favorite tool among mastering engineers, because, when paired with a spectral analyzer, it aids in evening out the curve. For instance, if the mix seems to be slacking between 1 and 4 kHz, then a multiband compressor can ignore up to 1 kHz with one band, compress 1-4 kHz with another, and then leave everything above 4 alone. This means, that, without affecting frequency ranges that may already be responding correctly, a multiband compressor can specifically lock in on target areas of the spectrum.
Multiband can be used in other situations too. By choosing which frequencies to compress on an individual track or even its parallel, the character of that instrument or vocal part can be given a point of focus without having to use an EQ. The result is a perception of greater sustain within the mix for that track, because it stays above the mix balance more, in the areas where it’s needed.
Using crossovers, a multiband array can be set up through a mixer. This can be a time consuming job but once accomplished, can be saved as a template for later use. Equalization and panning should be left alone during this setup, but stereo separation, and other forms of processing like saturation, excitement or compression can be used liberally. By gaining greater control over separate frequency bands, a more balanced mix can be obtained.