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3. Adding a sub-bass line

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Depending on your workflow, you might add some musical elements to your beat before you compose the bassline, but it’s possible to get straight into the bass as long as you’re sure you’ve correctly identified the key that your drums are tuned to fit with. We can use pretty much any soft synth to do this. Drag Dune CM (part of the CM Plugin Suite at filesilo.co.uk) onto a new MIDI track. 2

Click the Bank B button to get the initialised preset. Now we have a simple sawtooth tone that we can use to play along with the beat. The kick is in the pitch of E, and the snare is tuned to the same note an octave higher. Don’t worry if you don’t know yours as we can check the tuning by using Dune CM to play along with the beat. This confirms that E is the best fit, so let’s use that as the root note of our bassline. 3

Let’s turn our sawtooth-based patch into a weighty sub-bass. Start by renaming the MIDI track ‘Sub’. Change the Osc 1 waveshape to sine, set the amplitude envelope’s Attack to 8% and Release to 12%, and activate the Mono button in the Output panel. Sequence an E0 note so that the bass plays for the duration of the bar. (Check the sudio: Beat with sub.wav) 4

The level of a sine wave sub can be hard to gauge, especially if you’re working in an uncorrected acoustic environment or with speakers that don’t have a great low-end response. Let’s use Voxengo Span to make sure we’ve got our level right. We can see that the sub is a lot louder than everything else – bring its level down to -2dB to rein it in a bit. (Audio: Quieter sub.wav) 5

Depending on the acoustics of your room, the particular note the sub is playing could sound too quiet or loud, but if you take a listen on headphones it should be about right. The problem with just using a sine tone for the bass is that it only gives us energy in the very lowest octave. Let’s layer it with another synth to fill out the sound. Duplicate the Dune CM track, and call the new version ‘Bass Layer’. 6

Bring up the new Dune CM’s interface and change the Osc 1 waveform from a sine wave to a square. Square waves are full of odd harmonics, which will help us fill out the low end of the mix. Both Dune CMs are playing in the same octave, which means that both the sine oscillator on the Sub track and the square oscillator on the Bass Layer track will be at the same fundamental frequency.

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Set Osc 1’s Semi parameter to +12 to transpose it up an octave. The square wave certainly fills out the harmonics above our sub-bass, but it doesn’t sound very pleasant or have a lot of movement. That’s partially down to that fact that our bassline only plays a single note, but we can make it a bit funkier with some filter movement. 8

In the Filter panel, click the filter type, and select BP12 -> LP12 from the list that appears to get a band-pass filter. We can sweep this filter using an LFO to get a rhythmic effect. Click the Mod Matrix 1>12 button to bring up the Modulation Matrix. 9

Set the second row of the Modulation Matrix to Source: LFO 1, Destination: Filter Cutoff and Amount: +20. Now turn the Cutoff knob in the Filter panel down to 44%. This gives us a heavy rhythmic bass sound with a lot of weight and movement, despite the extremely simple sequence we’ve used. (Audio: LFO bass.wav) 10

Turn the synth’s track down from -2dB to -8dB. The problem now is that the mix is starting to sound both hot and muddy. Here we have a few options: we could turn down the bassline, but that would spoil the balance we’ve achieved, or we could stop running the track so hard into the clipper on the master, but that would make it quieter.

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There’s an alternative that allows us to maintain both the balance and the loudness. By sidechain compressing the bass with the kick and snare, we can make both sound louder. Add Live’s Compressor effect to the LFO bass track, and click the triangle at the top of its interface to bring up the sidechain section. Click the Sidechain button. 12

Set Audio From to the kick drum track, and bring the Threshold down to -30dB. Now the LFO bass ducks when the kick plays. Duplicate the Compressor and set the copy’s Audio From to the snare track. Now the LFO bass will duck when the kick or snare plays, helping our one-shots punch through the mix. We looked at sidechain techniques more thoroughly in last month’s Computer Music. (Audio: Sidechained bass.wav)