by Craig Anderton
There’s a saying that “You can never be too thin or too rich.” That may work for models, but it’s only half-right for keyboard synth bass: Rich is good, but thin isn’t. Looking for a truly corpulent bass sound that’s designed to dominate your mix? These techniques will take you there.
A common approach to crafting a bigger sound is to layer slightly detuned oscillators. However, that can actually create a thinner sound because slight detunings cause volume peaks but also, volume valleys. This not only diffuses the sound, but often makes it hard for a bass to sit solidly in the mix because of the constant sonic shapeshifting. Following are some layering approaches that do work.
Three oscillators with two pitch detunings. Pan your main oscillator to center, and set it to be the loudest of the three by a few dB. Pan the other two oscillators somewhat left and right of center, and detune both of them four cents sharp. Yes, this will skew the overall sound a tiny bit sharp; think of it as the synth bass equivalent of “stretch” tuning.
Dual oscillators with detuning. You can get away with detuning more easily if there are only two oscillators, as the volume peaks and valleys are more predictable. Pan the two oscillators slightly left and right of center, set them to the same approximate level, tune one oscillator four cents sharp, and tune the other four cents flat. If that’s still too diffused, pan them both to center, tune one to pitch, detune the other one eight cents sharp, and reduce the level of the detuned oscillator by -3 to -6dB.
Three oscillators with multiple detunings. If you must shift one oscillator sharp and one flat in a three-oscillator setup, consider mixing the two shifted oscillators somewhat lower (e.g., -3 to -6dB) than the on-pitch oscillator panned to center. This will still give an animated sound, but reduce any diffusion.
Three oscillators with layered octaves. This is one of the most common Minimoog bass patches (Fig. 1), and yes, it sounds very big. Adding a slight amount of detuning to the lowest and highest oscillators thickens the sound even more, as this simulates the drift of a typical analog synthesizer.
Fig. 1: This Arturia Minimoog V shot shows an archetypal Minimoog patch, with three oscillators set an octave apart via the Range controls. Note that the lowest and highest oscillators are tuned a bit off-pitch to add more sonic animation.
Two oscillators with layered octaves. While this doesn’t sound quite as huge as three oscillators with layered octaves, removing the third oscillator creates a tighter, more “compact” sound that will cede some low-end territory to other instruments (e.g., kick drum).
Sub-bass layer. Drum ’n’ bass fans, this one’s for you! Layer a triangle wave one octave below any other waveforms you’re using. (You can also try a sine wave, but at that low a frequency, a little harmonic content helps the bass cut through a mix better.) For a really low bass end, layer three triangle waves with two tuned to the same octave (offset one by +10 cents), and the third tuned one octave lower and offset by -10 cents. Sub-bass patches also are excellent candidates for added “punch,” which provides the perfect segue to . . .
There are two main ways to add punch to a synth sound.
Percussive punch. This requires adding a rapid amplitude decay from maximum level to about 66\\\% of maximum level over a period of 20-25ms (Fig. 2, top).
Fig. 2: The upper envelope generator picture from Cakewalk’s Rapture shows a quick percussive decay that adds punch. The lower envelope setting achieves a more sustained punch effect by kicking the envelope full on for a couple dozen milliseconds.
To emphasize the percussiveness even further, if a lowpass filter is in play, give its cutoff a similarly rapid decay. However, for the filter, bring the envelope down from maximum to about 50\\\% of maximum over about 20-25ms.
Sustained punch. This emulates the characteristics of the Minimoog’s famous “punchy” sound. (Interestingly, the amplitude envelopes in Peavey’s DPM-3 produced the same kind of punch; after I described why this phenomenon occurred in Keyboard magazine, Kurzweil added a “punch” switch to their keyboards to create this effect.) Sustained punch is simple to create with most envelope generators: Program an amplitude envelope curve that stays at maximum for about 20-25ms (Fig. 2, bottom). This is too short for your ear to perceive as a “sustained sound,” but instead comes across as “punch.”
If your soft synth doesn’t do hard sync, there’s a nifty trick that gives a very similar sound—providing you can add distortion following the filter section.
Fig. 3 shows Rapture set up for a hard sync sound on one of its elements.
Fig. 3: Feeding a lowpass filter with a reasonable amount of resonance through distortion can create a sound that resembles hard sync.
Note the setting of the Cutoff, Reso(nance), and BitRed controls (Bit Reduction is set for a Tube distortion effect, as shown in the label above the control). The envelope shown toward the bottom sweeps the filter cutoff from high to low. As it sweeps, the filter’s resonant frequency distorts, producing a hard-sync like sound. The crucial parameter here is resonance; too little and the effect disappears, two much and the effect becomes overbearing . . . not that there’s necessarily anything wrong with that . . .
For most big synth bass sounds, a sawtooth wave passed through low-pass filtering (to tame excessive brightness) is the waveform of choice. As a bonus, if you kick the lowpass filter up a tad more, it brings in higher harmonics that add a “brash” quality.
For a “rounder” sound that’s more P-Bass than Synth Bass, try a pulse waveform instead (Fig. 4).
Fig. 4: Remember Native Instruments’ Pro-53? It's one of many soft synths that provides pulse waveforms. Better yet, a pulse width control determines whether the pulse is narrow or wide.
I prefer narrow pulses (around 10-15\\\% duty cycle), but wider pulse widths can also be effective. The same layering techniques mentioned earlier work well with pulse waves, but also experiment with layering a combination of pulse and sawtooth waves. This produces a timbre somewhere between “tough” and “round.”
Triangle and sine waves have a hard time cutting though a mix because they contain so few harmonics. If you want a very muted bass sound, use a waveform with more harmonics like sawtooth or pulse, then close a lowpass filter way down to reduce the harmonic content. This provides a rougher, grittier sound due to the residual harmonics that remain despite the filtering. However, while triangle waves aren’t necessarily great solo performers, they’re excellent for layering with pulse and sawtooth waveforms to provide more low-end girth.
Just because you’re playing in the lower registers doesn’t let you off the hook to add as much expressiveness as possible. Some programmers get lazy and do the default move of programming the mod wheel to add vibrato, but that’s of limited use with bass. If you want vibrato, tie it to aftertouch, and reserve the mod wheel for parameters where you need more control over the sound.
Creative use of modulation could take up an article in itself, but these quick tips on useful modulation targets will help you get started.
Filter cutoff. This lets you control the timbre easily. If the filter is being modulated by an envelope, assigning the mod wheel to filter cutoff (Fig. 5) can also create a more percussive effect when you lower the cutoff frequency. Try negative modulation, so that rotating the mod wheel forward reduces highs.
Fig. 5: Cubase’s Monologue synth makes it easy to assign the mod wheel to filter cutoff as one of the filter modulation sources (circled in red).
Volume envelope attack. To transform a sound’s character from percussive and punchy to something “mellower,” edit the mod wheel to increase attack time as you rotate it forward.
Layer level. Assign the mod wheel to bring in the octave-lower layer of a sub-bass patch. This pumps up the level and really fills out the bottom end.
Distortion. Yeah, baby! Kick up the distortion for a bass that cuts through the mix like a buzzsaw, then pull back when the sound needs to be more polite.
Resonance. I’m not a fan of highly resonant synth bass sounds (they sound too “quacky” to me), but tying resonance to mod wheel provides enough control to make resonance more useable.
Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.
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