Practical Mixing tips #2: Ride the Bus: Notes on aux channels, busing and audio routing
In this instalment we’ll talk about using aux channels (sometime called buses) to mix instead of just mixing with the individual channel strips containing instruments and vocals. This is another case where you can find very complicated info online about aux/bus/return/foldback etc. For the purposes of this article, we can say an aux and bus channel are basically the same thing. i.e. A place to send audio. You can’t record into an aux/bus but you can process audio there. Also the term bus is often used as a verb eg: “Let’s bus all these vocals to an aux track”.
The benefits of mixing this way are huge:
1) Minimizing tracks. You can turn many tracks, like 50 or more into maybe 10-12, which is easier to wrap your head around.
2) Processing similar things as a group rather than individually. If sounds are bused together, you can apply one reverb to the group, or EQ all of them at once, squash them all with compression etc. OR Even better, use the send function to send signal from the aux/bus group to another aux channel acting as a master reverb for the song. This also taxes the processor less heavily than putting effects on individual channel strips so it’s easier on the computer’s brain and your own brain.
Leading to the next benefit…
3) Using master effects channels! You can set up an aux channel to have a main effect like reverb live there. You can send audio from of any instrument channel or aux/bus to this master effect aux channel, giving the song a sort of sonic glue, and making it sound like everyone was performing in the same space (even if they weren’t). If you go name your band Sonic Glue - a simple mention in the liner notes is fine, thanks.
Here are some examples using Logic X, which is my go to DAW, but these look pretty similar in pro-tools or whatever you may use.
DRUM MIC CHANNELS
Above are several drum mics: kick front and back, snare top and bottom, stereo oveheards and room mics. This was recorded at Lincoln County Social Club, and John who runs the studio likes to have fun with Mono mics in strategic places. (Check him out he does great work!) http://lincolncountysocialclub.com
On this session the “Mono Hi” mic sounded so great, that it ended up being the main sound of the kit for this mix, with the other mics coming in as support.
13 drum mics is a lot to deal with, so we can bus them to aux channels like the above. Here we have grouped all the similar mics together. (Both kicks together on bus 11, snares together on bus 12, rooms together on bus 16 etc). To do this change the output from Stereo Out (default) to your desired aux channel. If you compare the two screen shots here, you should be able to follow the chain we have happening.
AUX CHANNELS
We’ve also outputted all the drum aux channels to bus 1, which contains the entire drum kit. This is handy to turn all the drums up or down if you need to. And we’ve also applied compression to the drum kit as a whole. If you are wondering why the toms are not eq’d it’s because the audio has been muted elsewhere, so these mics are not in the mix. As a side note for mixing drums, just because there are 13 mics to work with doesn’t mean they all make it into the final mix. There was plenty of tom action in the room mics, so I left the toms out.
In the above, we are also using the send function to use master effects. On the far right of the aux channels there is a short room verb and “Shimmer verb”, which is a longer plate verb. The snare drum, electric guitar and lead vocals were all sent to the bus 17 - the room verb. You can also control how much of each sound goes to the effect channel. In this case there is quite a bit more snare is going to the room aux compared to the guitar and vocals.
The backing vocals (marked VOX AHH) required a longer bigger reverb for this mix, so they are sent to bus 18 - the plate verb.
Using an aux track for verb also lets us EQ the reverb channel and indeed I had to knock out a bunch of low frequency that was clouding up the bottom end of the mix. This very handy trick can’t be done if you put 15 different reverbs on various individual tracks , doing it that way tends to create a lot of frequency build up that’s almost impossible to get rid of.
Start playing about with some aux channels using effects, and you’ll see what I mean! And feel free to leave comments, if you have questions, or think I’m full of baloney.