The Art of Synth Soloing - A Little Rough Around the Edges

July 5, 2013

Back in the April column, I left you with a lead sound that faded into harmonics via a controller, and said we were on our way to emulating classic guitar feedback. Let’s continue with that exploration. The logical next step is to dirty up the sound a bit—but not too much—to bring our synth playing closer to the role that distorted lead guitar has played in music for decades.


Ground Rules

These are deep waters we’re entering, and guitar players can and do go on ad nauseam about the nuances of distortion. I only want to dip our toes in, so the ground rules for this month are:

We want a subtler addition to our tone. All-out fuzz and over-the-top grind are cool, but they tend to take over your sound and playing. Such sounds usually are the product of hard clipping, where the tops of the waveform have been flattened out severely. It doesn’t much matter what waveform you feed into these types of sounds, the distortion itself becomes the tonality, and your sound gives up most of its character to this effect. Also, it becomes difficult to play faster lines with any distinction, and forget about playing higher up on the keyboard, as the aliasing and intermodulation distortion (especially when pitch-bending) becomes pretty nasty. Check out the online audio clips to hear what I’m talking about.

Our “dirt” should respond to our playing dynamics. In guitar terms, overdrive is the even harmonic-based sound of an amp that clips in a gentle, rounded fashion, called soft clipping. The tops of the waveform are altered but not completely flattened. When this happens dynamically, the softer playing is not changed (as much) and the clipping increases as you feed the effect a stronger signal. This soft clipping adds some edge to your sound without taking over. For a synth lead you often don’t want your sound itself to have too much dynamic range, as you can get lost in the mix while soloing. So we don’t need the amp or filter to respond significantly to velocity. But by making your effects respond to velocity you get to control your overdrive dynamically, getting dirtier as you dig in harder.

 Fig. 1. Applied Acoustic Systems’ Ultra Analog offers a variety of filter overdrive types. Fig. 2. Spectrasonics Omnisphere also provides an abundance of filter types and characteristics.
Fig. 3. Ableton Live’s Saturator includes a waveshaping mode.
 Fig. 4. Logic’s Distortion plug-in offers basic input and output gain staging, plus a tone control.

Just a Little Edge

Before we go to effects, there are some synthesis-based ways to give our sound a little attitude. See if your synth has any controls for boosting the signal going into the filter, or a feedback loop, or a filter drive parameter. Logic’s ES2, U-he Zebra 2, Applied Acoustics Ultra Analog (see Figure 1), Reason’s Thor, and many other software (and hardware) synths have this feature. Other synths may offer a filter type that already models some amount of saturation or drive. Figure 2 shows the many choices available in Omnisphere. Can the parameter be a modulation target? If so, use velocity to increase the depth or intensity of the effect.

Does your synth have an external audio input? If so, try routing an output from the synth back into itself. On a hardware synth, try using the headphone output (this won’t work on synths where plugging in headphones mutes the main outs and there’s no way to override this behavior). For a soft synth, you can set up a bus output in your host software, which you can then feed back into the synth’s input. This is a classic technique that I first learned from Jan Hammer’s work, where he connected the low output of his Minimoog back into the external input and set the level to clip just slightly. This fattened up the sound nicely, and is now even documented in the manuals for most Moog synths.

Waveshaping can also add some edge to a sound, but you need to use it very sparingly and find a shape or preset that’s not too over the top. Some classic hardware synths like Korg’s O1/W and Prophecy offered it as part of their voice, as do Cakewalk Z3ta+ 2 and Spectrasonics Omnisphere; today’s Korg Kronos, Propellerhead Reason, Ableton Live (see Figure 3), and many others offer it as an effect type. Whenever possible, set up velocity to modulate the depth of this drive/waveshaping.

Digging in the Dirt

There are two approaches to adding effects for overdrive/distortion: using a dedicated effect (including models of classic effects pedals), or using a complete guitar amp modeling setup such as a Line 6 Pod or IK Multimedia’s AmpliTube software. While both can produce wonderful results, I recommend you start with the dedicated effect for synth leads. Why? Many guitar amp models include speaker/cabinet emulations, and these roll off frequencies and color the sound based on the frequency range of a guitar, not the full-range output of a synthesizer.

To produce overdrive or distortion, the input to an amplifying device was overloaded, producing additional harmonics and color. Most effects emulate this by having an input gain control and another output level control to compensate for the increase in volume that occurs as you raise the input level. Note that the input control may be labeled as drive, gain, overdrive, crunch, fuzz, or other things besides “input gain.” Not to worry. Figure 4 show this in Logic’s very basic Overdrive effect. The basic idea is: The more you increase the input gain stage, the more you’ll want to decrease the output stage. We want more “attitude” for our sound when we kick it in, not more volume. 

So look through your synth or soft synth or DAW and find the category of distortion, or overdrive effects. Pick something as an insert effect in your synth or DAW. If it has presets, take a tour through them. As you call up the presets, examine how they’ve set the controls, paying close attention to the amount of gain or effect being introduced at the front of the signal chain. This is the critical input overload stage that we want to set to taste, not going so far as to fuzz out our playing. 

If you find that the effect is drastically changing the thickness and tonality of your sound, look to see if it includes some form of speaker simulation and turn that off. If that doesn’t help, you should set it up on a bus in your DAW, or as a master effect in your synth, so you can blend the wet/dry mix via the send level to your bus, or the level of the bus return. This way you can add a little of the effect’s sizzle without sacrificing all the frequencies of your original sound. With this routing I can use the most aggressive, high-gain effect and tame it to my needs, and even accept the results of an included speaker simulation. Finally, if at all possible, set the master effect’s wet/dry mix, send, or bus return to be modulated by velocity so your fingers can interact a bit with the amount of overdrive added. In a DAW this may need to be done via automation, not just MIDI learn. As always, experiment and enjoy!

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