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Modular Synthesis (Part 3)

Bass Sounds

This month, Steve Howell concentrates on the lowest two octaves, and comes up with some interesting variations on the bass synth theme.

Strong bass sounds have always been important to musicians as a means of providing a solid basis to any piece of music, and a weak bass end will nearly always have a detrimental effect on the rest of the piece, however good the rest may be. To illustrate this, try turning the bass control down on your hi-fi - I think you will find that the depth and strength will disappear and this probably accounts for the fact that so much modern music (especially dance music) has a very strong bass end.

For synthesists, it's important to set up a good bass sound as this is usually the part that will be laid down first in the multitrack process, especially if a sequencer is being used.

Figure 1

The most simple patch can be found in Figure 1. Here we have one or more VCOs being fed into a VCF and then into a VCA, both of which have an EG applied to their CV inputs for independent shaping. You can use as many VCOs as you like and they can be tuned to unison, an octave apart or whatever. Normally I use three VCOs and for a deep bass sound I tune two VCOs to unison and the other an octave up, but for a sharper bass sound tune VCO1 and 2 to unison an octave down. For added depth I like to use at least one square-wave with a variety of waveforms from the other VCOs dependant on the effect I want. Two sawtooth waveforms will give a rich texture whilst using a pulse-wave will give you a sharper, Clavinet-type bass sound. Using pulse width modulation will enhance the detune effect but care has to be taken not to make the sound too 'swirly' which can sometimes happen if the detune and PWM effects are set to extremes. The filter and EG controls can be altered to suit and this patch should serve a variety of purposes from deep pedal notes to high-speed sequencer riffs, and these effects are available to the owners of even the simplest synthesiser. One point to watch out for, however, is that when VCOs are tuned to unison they can sometimes 'null' on you - that is, the phase relationship of two very closely tuned VCOs can sometimes cancel each other out, leaving a momentarily weak sound. This happens totally at random, so to retain that fullness I suggest you detune the VCOs quite considerably. On the other hand, you can use just one VCO, and this should give a clear, uncluttered bass sound. Remember that just because you have the hardware, doesn't mean you have to use it, and simplicity can often be more effective. Thomas Dolby said recently that he prefers to use a single VCO for his bass sound, but that doesn't prevent him having a solid bass sound in his music. Afficianados of the Jan Hammer, Joe Zawinul school of synth bass playing will probably prefer to have that rich, phasey, detuned VCO effect that two or more VCOs will give you, so it's really a matter of taste. There are no hard and fast rules.

That, then, is the basic method of producing bass sounds. Experimentation with just that patch will provide you with some 'fruity' (for want of a better word) bass-end sounds but there are a number of ways in which you can produce some less commonly-used bass textures which require a little more thought (and hardware!). The extra effort is well worth it if you want to avoid the usual cliches.

Simple Extension

Figure 2

First, as a simple extension to Figure 1, try feeding an unprocessed sine-wave from another VCO directly into the VCA, as in Figure 2. This can be particularly useful on high-resonance VCF settings where the depth tends to disappear - the extra VCO will make up for this. You might like to try routing the sine-wave into a separate VCA/EG - this will enable you to have a separate envelope for the two 'channels', so that the basic sine-wave will give you the basic bass sound, and then the filtered VCOs can be shaped to give a punchy front-end to the sound. Many varied synth and acoustic/electric bass sounds are possible using this method, and if you find the single sine-wave a bit static you could route that element into a chorus unit or a mild flange to give it more movement.

Another way of producing an interesting bass sound - particularly good for fast sequencer riffs - is to employ a similar technique to that in Figure 2, but substituting a noise generator in place of the VCO. In this way, you can add a percussive 'chiff' to the attack portion of the sound which could, if you so desired, be processed by another device such as a flanger. A deep, slow flange will give you the Japan/Duran Duran-type sequencer sound, but a slow filter sweep on just the noise element could give you a very similar effect.

Sample And Hold

Figure 3

Another technique you might like to experiment with is shown in Figure 3. Here we are stepping through a Sample and Hold (S/H) device with the trigger output of the keyboard. The random CV output from the S/H is routed to just one of the VCOs and the modulation level is set to give a slight random detune effect. The knack with this sound is setting the modulation level; too much and the effect will be almost unusable - too little will make the effect so subtle that by the time you add the other instruments on top you probably won't even notice it. When set up properly, however, you can create some very interesting and realistic fretless bass sounds á la Mick Karn, especially with lots of pitch-bend and vibrato. It can be equally effective on sequencer riffs as well, but here the trigger input to the S/H is derived from the sequencer's gate or trigger output.

If your VCOs have a Sync facility there are a number of additional possibilities available to you offering some very distinctive bass sounds. The most elementary sound using Sync is simply to tune the VCOs at a variety of intervals with the Sync switch 'on' (or with the Sync in and out sockets connected with a patch cord), which will give you a variety of textures depending on the waveform and interval selected. Wide intervals with a square-wave will let you create some fascinating PPG type, digital sounding textures but if you find these too delicate (as they sometimes can be) do as we did in Figure 2 where the sine-wave was also used to add some depth to the sound. Alternatively, you could use another VCO detuned against the two Synced VCOs and routed via the VCF for a richer sound. This will give you the best of both worlds as the Synced VCOs will give you the unusual waveshapes and the third VCO will give you the 'fruitiness' of detuned VCOs.


Figure 4

Of course, we are all familiar with the Sync-sweep sounds so beloved of many synth players but I feel care has to be taken to avoid the usual cliches using this sound. The patch for Sync-sweep is given in Figure 4. This allows you to vary the frequency of VC02, and as its pitch changes so the harmonics in the resulting waveform are 'torn apart' giving this characteristic sound. The control device could be anything and the simplest you could use is an LFO set very slow, but you could use an EG, giving you a Sync-sweep effect that varies in accordance with the ADSR controls. Alternatively, you could use an S/H as in Figure 3, which would give you a slightly different waveform on each note. If you replace the S/H with a sequencer and step through that instead, you can reprogram the waveshape, whereas with the S/H the waveshape will change in a random fashion.

As always, there are a number of points to watch out for when recording bass sounds and in the technique you employ to play them. First, as with nearly all sounds, the lower down the register you go the longer the envelope times will be, so it might be a good idea to use a Keyboard Follow on the EGs if you have such a facility, but to be honest it is not essential for most bass sounds.

Useful Tips

If, however, you feel your bass sound is still somewhat lacking in the necessary 'welly', here are a few tips which I think you might find useful.

1: Try using a square-wave as the basic waveform for your sound. The harmonic structure of a square-wave is particularly suited to low sounds that require depth, so try mixing it in with other waveforms.

2: Try lowering the resonance setting of the VCF. The response of most lowpass filters is such that the fundamental and lower harmonics are attenuated below the cutoff point of a high-resonance setting and this can severely 'weaken' any bass sound. If a high-resonance setting is essential, try mixing in the raw sine-wave as in Figure 2.

3: Chorus or a mild flange will animate the sound if it's sounding a bit static. Stereo chorusing via the effects send on the mixer - with the straight sound on one side and the chorused sound on the other - will spread the sound out and give it an extra sense of thickness. This technique can also be usefully employed to alleviate the problem you sometimes get when a bass note occurs at the same time as a bass-drum beat and you end up losing the definition of both sounds. To rectify this, spreading the bass sound hard left and right with chorus or flanger, with the bass-drum dead centre, will help to retain each instrument's clarity. You should have a tight and punchy rhythm section which can be very powerful if you are using a driving sequencer and drum computer rhythm.

4: Try boosting the bass end on the mixer. Simple though this sounds, many people struggle for ages trying to get the sound right at their synthesisers where a simple tweak of the EQ will give them what they require.

5: Double-tracking the bass part will also create a dynamic sound. Many bass-players do this and there is no reason why the same technique shouldn't be used with synth bass parts. A band renowned for their synth bass sound is the Thompson Twins, and I believe they utilise this technique. If you are unable to double-track your bass line, either because it is of a very improvised nature or because you are using a sequencer which is unable to be driven off a click-track (or because you don't have enough tracks on your tape-machine) you could try using a fast delay in the region of 20ms or so as this will give a similar effect.

6: Using a compressor will also add a degree of 'punch' to your bass sound. Again, bass-guitarists use this technique as it evens out the envelope and tightens the sound up considerably, so why not try it on your synthesiser?

After recording your bass part, and having added further instruments over the top of it, you might find that what was once a solid and punchy sound on its' own doesn't sound quite so good with everything else. If this is the case, there is no reason why you shouldn't use any of the methods outlined above with the recorded bass part on tape to improve the sound; so if you can, try and keep the bass part on a separate track of tape so that you can mess around with it later without affecting anything else when mixing down.

Playing Techniques

As for playing techniques, there are no hard and fast rules. It all depends on the piece you are working on, and all I can suggest is that you listen to bass parts, be they synth, electric or acoustic, to see how they are constructed. Different styles of music have different styles of bass playing, but one thing you can be sure of is that when drums and bass are playing together, the bass usually appears together with the bass-drum, especially on downbeats, so if you are programming your bass and drum parts into a MicroComposer and drum-computer, that's worth bearing in mind, I feel. If you are playing with a 'live' drummer then that sort of interaction often takes place naturally, but it's worth thinking about nonetheless. When a band is accused of not being 'tight' it's usually because the interplay between drummer and bass-player is sloppy and this can have a profound effect on the feel of the music and out interpretation of its 'solidness' so it's important to get this element right before moving onto the chordal and melodic overdubs. After all, you can't expect a house to be very substantial if the foundations are weak.

And with that stunning analogy, I leave you to fiddle with your bottom ends until next time, when we'll be looking at percussive noises.

Series - "Modular Synthesis"

Read the next part in this series:

All parts in this series:

Part 1 | Part 2 | Part 3 (Viewing) | Part 4 | Part 5 | Part 6 | Part 7 | Part 8 | Part 9 | Part 10 | Part 11 | Part 12

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Talking Shop

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Roland System 100M

Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.


Electronics & Music Maker - Mar 1984


Synthesis & Sound Design


Modular Synthesis

Part 1 | Part 2 | Part 3 (Viewing) | Part 4 | Part 5 | Part 6 | Part 7 | Part 8 | Part 9 | Part 10 | Part 11 | Part 12

Feature by Steve Howell

Previous article in this issue:

> Talking Shop

Next article in this issue:

> Roland System 100M

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