Multiband Compressor Tips
A multiband compressor will let multiple frequency ranges (bands) have different compression settings. Compressor's typically affect the entire range of frequencies.
Audio engineers use these for many different purposes. Here are 3 simple problems where using a multiband compressor could help you out.
One major use would be on a group of drum tracks. A common problem for many is that your kick drum is too strong and making your mix sound muddy or have too much rumble. You could compress the low frequencies of the kick and leave the high frequencies of the other drum sounds uncompressed. If you were to use an EQ, then it would start to actually remove the low end of the kick. Compressing the entire low end of the drum bus would just put some control over it without deleting all the other frequencies.
A second use would be making vocals throughout a song sound even and consistent. When recording vocals, there is a huge dynamic range (highs and lows in db) when the singer moves closer and further from the mic. The chorus and verses will most likely fall into close but separate frequency ranges. Use a multiband compressor by placing a band for the chorus separately from a band for the verses. Adjust accordingly so the vocals are consistent throughout the whole song.
Toms and Snares as well as other drum elements are sometimes prone to leave a ringing noise. Instead of notching out the sound entirely with an EQ. Find the ringing frequency range, then use a band from the multiband compresor to control the ring alone. Sometimes frequency-specific compression will work better then just notching out the problem area.
The multiband compressor really is a multifaceted tool. These are some practical uses. It seems to work best on complex mixes or complex instruments like piano. It's a great tool to make late, last minute changes in your mixes.