A multiband compressor is a powerful tool for controlling dynamics. The signal is split into 3 or more frequency ranges and processed independently. This is different from a standard compressor which operates on the entire frequency range at once.
Standard compressors are great, but sometimes you’ll find that with any significant amount of gain reduction you start to get a very dull sound. With Multiband compression Each frequency range has an independent compressor so a source that has a lot of mid frequencies might end up with very little compression in the high frequencies, maintaining the brightness of the source. [read]