Wednesday, August 27, 2008

Using a Bus to Route Effects in Ardour

When using computer audio effects, one must always bear in mind that your poor computer has to calculate the effect output everytime you play back your tracks. So when you go too crazy with effects, your computer will probably seize up, roll-over and die! To save your computer, it is important to use buses to route repeated effects in Ardour.

Okay, maybe that sounds like complete gibberish... but please bear with me and you'll soon understand what I mean. Let's take an example of a multichannel recording of a drumbeat in Ardour (i.e. one channel for snare, one for the kick drum, etc.). For each drum, you would want to add certain effects like an EQ, reverb, and compressor. One way to do this is to add the effects to each channel like in the figure below.

Since you would want the same sounding reverb on each drum, your poor computer has to calculate the same thing multiple times. This is unnecessary because you can create a bus and route all the drum channels to it and then only put one reverb on the bus. This method achieves the same sound whilst your computer does less. You can do this by following the steps below:

Firstly, you need to create a new bus. Go to Session, and click on Add Track/Bus. Configure the window that appears to look like the one shown below. i.e. select Busses and Stereo.

You now need to route all your drum channels to the bus (I have renamed mine to be DrumBus). You do this by right-clicking on the black rectangle below the volume fader (this is called the "post effects" for the track). A menu should appear and you must select New Send... Configure yours to look like the one shown below. You do this by firstly adding an output (click the Add Output button) and then selecting where you want the output to go. In this case you choose DrumBus/in1 and DrumBus/in2 from the Ardour tab on the right of the window.

Since you have rerouted the output of the each drum track, it no longer needs to be connected to the Master Bus. So disconnect it by clicking on the Output button (just above the Comments button) at the bottm of each drum channel and select Disconnect. Your drums should all be sounding through your Drum bus. This means that if you adjust the DrumBus volume, all the drums' volumes should change. It also means that any effects you use on the drum bus will be applied over the whole drum kit. The figure below shows how the bus greatly reduces the amount of reverb effects used.

Note that I have left the EQs and Compressors in each channel and not on the bus. This is done because the EQs and Compressors are set differently on each drum and thus cannot be applied to the whole kit via the bus. I hope you found this tip useful, and that your computer will also appreciate it :). A special thanks goes out to Jakob Lund for suggesting this method of adding multiple effects.

Other posts you might find interesting:
Audio Recording in Ubuntu Studio - Part 3: Adding Effects to the Ardour Drumtrack
My Favourite Linux Audio Effects
An Overview of Compression
Panning for Gold : How to Pan Tracks
Mastering Tips: A Picture Says a Thousand Words

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