Multi-Bus Mixing

This sophisticated mixing technique uses more than one mix bus for differing types of sounds. These multiple mix buses are then combined in a final stage to create the full mix. The concept stems from the common practice of inserting a compressor on the mix bus of a console. Gradually, as you add channels to the mix, the compressor kicks in and starts compressing the whole mix.

The trouble starts when you’ve added too many signals and the compressor no longer is helping the sound glue together but rather starts shrinking the sound stage, making everything sound smaller. Also, when a mix is coming close to the end and various tweaks are being applied, these can upset the balance of the compressor operation, throwing the whole mix out of balance.

Most often this happens with the larger elements in a mix such as the lead vocal, bass, and drums. If, at the end of a mix, it feels like the lead vocal needs to come up a bit, this can force the mix bus compressor to kick in more and hurt the sound of the bass and drums. Multi-bus mixing overcomes this issue by keeping some key sounds isolated from each other in their own mix bus with their own compressor. Think of it as large scale subgrouping.

Note Michael Brauer (www.mbrauer.com) has also popularized this mixing technique on Internet blogs and forums. He has been very generous in sharing his techniques with aspiring recording engineers. If you are interested in learning more about his techniques, please visit his website and peruse the Q&A section.

Here’s one way it could work:

1. Create two or three VST Output buses. These will be your mix buses.

2. Name them as they relate to the sounds that will be routed to them. Think of the mix in terms of sonic types. Typically, the drums and bass will get a mix bus. You could make a second bus for midrange instruments and a third for vocals.

3. Create a fourth mix bus called Final Mix or something appropriate; this will be where everything combines into one final mix.

4. If you are using Control Room, make sure that the final mix bus is the Main Mix so that it will be routed to the Control Room mixer. Also, none of the mix buses need to be connected to any device ports. They are virtual mix buses. (See Figure 14.5.)

5. Create sends on each of the first three mix buses routed to the final mix, THE MIX. You must use sends because VST Outputs cannot be directly routed to other VST Outputs. Using the sends allows you to combine them all together on the final mix bus.

Figure 14.5 VST Outputs for multi-bus mixing.

Caution Do not place any processing on this final mix bus because this will defeat the basic purpose of the multi-bus technique. When you are comfortable with the technique, you certainly can apply processing on the final bus, but getting used to this scheme takes a bit of time at first. I will use a brick-wall limiter and dithering plug-in on this final mix when rendering client files as it is necessary to output files for CD and MP3 properly dithered and at a decent level, but that’s all.

6. Set the sends level to unity (0 dB). The three mix buses will be combined at the same level to the fourth and final mix bus. (See Figure 14.6.)

7. Insert compressors and even equalizers that have a tone that is complementary to the group of sounds. For example, a Fairchild-type compressor and Pultec-style EQ can sound wonderful on bass and drums. The midrange elements might need a slightly faster compressor such as an SSL-type. This is purely a matter of taste, and experimentation is the only way to find what works for you.

8. Route the various channels to the appropriate mix bus and blend the mix together, achieving some amount of compression on each mix bus.

9. Once you have a basic blend going on with some compression certainly in the bass and drum bus, try turning up the lead vocal a decent amount and notice how the balance changes. It is very different from the traditional single mix bus compressor approach. The drum and bass balance should not be disturbed, and the vocal can easily come up in level.

Once you have this multi-bus mixing technique running well, you will discover that you have more versatility to make changes as you move along through the mixing process. Making major changes will have less effect on other elements in the mix that are sounding good, giving you more elbow room to be flexible.

Figure 14.6 Sends from each mix bus to the Final Mix.

Note Note that although this technique is very versatile, it won’t work on every mix. Sometimes the traditional approach is the way to go, and by no means are there ever any rules in mixing. The sophisticated routing that can be accomplished in Nuendo allows for this type of flexibility.