Group busses are a versatile and useful mixing technique. They’re often used in a variety of different situations:
- Distorted guitar stacks. It’s quite common to layer or doubletrack (or tripletrack or quadrupletrack) distorted guitar parts in order to make them sound bigger. Sometimes the layers are all recorded with the same setup (same guitar, same amp, same mic position, etc), but it’s just as common that the layers are recorded with different setups. The layers blend to form a composite guitar sound that the listener hears as a single diffuse part. Because all these layers function as a single part, it often makes sense to treat them as a single channel when mixing the bigger picture. By using a group bus, the layers can all be treated as one. This means that when you’re fitting the guitars in the context of the rest of the mix, you can set the level and tone of the guitars as if they’re a single part.
- Backing vocals. Much the same as distorted guitars, it’s common to treat layered backing vocals as if they’re a single sound source. This is especially useful when there are several layers that are singing the same words with the same rhythm. Unlike layered distorted guitars, it’s also common the different layers of backing vocals to be singing different harmony parts. Another difference is that backing vocals often benefit from some compression (distorted guitars often already have flat dynamics due to the distortion). When dealing with backing vocals, it’s often useful to compress each individual channels as well as the group bus. That way, each compressor can work gently while still resulting in a smooth and consistent sound.
- Pads. While not as commonly spoken about, grouping pads can be very useful for the same reasons as distorted guitars and backing vocals. Some particularly interesting effects can be created by combining several layers of different pulsing pads and then compressing the group. Done well, this will produce a texture that is more consistent in level but is constantly changing in tonality.
- Drum kit. This is a huge topic! The way drums and compressors interact can be quite complex. The sound is influenced by a variety of factors, ranging from the way the kit is played to the selection of kit components to the choice of miss and recording medium to the design and settings of the compressors. Like backing vocals, it’s common to compress individual drums in addition to compressing the drum group bus. Used lightly, drum group compression can give the whole kit a sense of glue and life and density. Just remember not to overdo it – too much compression will flatten your drums and make them difficult to work into the mix!
- Kick and bass. This is a technique that has been used subtly for some time, but has recently become more fashionable with modern dance music. By grouping the kick and bass and applying strong compression to that group, the bass will duck slightly when the kick is sounding. This will make the low end of the mix more compact and solid. This is now commonly taken to extremes with the use of side chain compression – instead of using a group bus, the bass is processed with a compressor that is keyed (‘side-chained’) from the kick.
Group busses are most useful when you have several tracks that all perform a similar function in the mix and you want to either glue them together or otherwise treat them as a single unit. Of course, you can group anything you like. It’s important, however, to keep in mind that sometimes it doesn’t make sense to use group busses. Often it doesn’t make sense to group tracks that aren’t related to each other or need to remain separate.
On the other hand, you might find some interesting sounds by using group busses in unusual ways…