Tech Tip:Realistic Guitar Emulations with Samplers
By Craig Anderton
I’ve done a lot of seminars in my time, and once I found myself in Nashville doing one on synth programming. Someone asked how to get a convincing guitar sound, and after thinking about it, I suggested that hey, you’re in Nashville—hire a guitar player!
Seriously, nothing sounds or plays like a guitar. But many keyboard players don’t play guitar, or don’t have someone on call who can record a part. So if you’re a keyboard player but would like to add a guitaristic element to your music, read on.
There are two main types of guitar playing, rhythm (chord-based) and lead (single note-based). Of the two, rhythm guitar is much harder to emulate because of how guitars are voiced and strummed. Guitar voicings tend to be "wider" than piano voicings; for example, consider a simple E major chord on guitar, and where the notes would fall on a keyboard.
Furthermore, rhythm guitar often combines open strings, which have a long decay, and fretted strings, which have a shorter decay. And as the strings are strummed, they don’t all sound at the same time.
One option for a convincing rhythm guitar part is simply to forego the keyboard and use sample CDs. There are several with good strummed, fingerstyle-type patterns, such as Big Fish Audio’s Acoustic Legends, Sony’s Acoustic Excursions, and Ilio’s Fingerstyles. Also note that there are sample CDs with sampled power chords (e.g., my own Technoid Guitars). These can be effective for simple rock tracks, but usually lack the variations and strums of a "real" guitar part. Still, they can work for non-critical applications.
A different option is the Virtual Guitarist VSTi plug-in from Steinberg, which delivers the goods for "rock"-type strumming and is easy to make fit with a song. Both acoustic and electric versions are available. Also, the aforementioned Acoustic Legends includes samples of up-and-down strummed guitar chords, mapped on a keyboard in such a way that it’s fairly easy to create convincing strummed parts.
Lead guitar lends itself well to synthesis, because the gestures involved in creating a single-note solo—pitch bending, vibrato, and sometimes, rapid-fire licks—are part of a synth’s standard repertoire. Also, when overdriving an amp, a guitar’s waveform will clip and "flat top," producing a more pulse-like waveform.
Pitch manipulation, either by a vibrato tailpiece or finger vibrato, is a guitar trademark. With synths, the pitch bend wheel is your tool of choice; a mod wheel controlling LFO vibrato produces a periodic effect that just isn’t guitar-like.
When imitating tailpiece effects (like "dive bombs"), remember that these primarily bend pitch down, and can bend up over only a limited range (e.g., a half step). With manual vibrato, a typical gesture is to bend pitch up and then add vibrato—again, a perfect job for manipulating the pitch bend wheel manually. It takes a little effort to learn the finger motions necessary to add vibrato, but it’s worth it. The slight irregularities add interest to the sound.
Another common lead guitar effect is holding a note so that it sustains, during which time the timbre changes (sometimes just from natural changes in string harmonics, sometimes from going into feedback). For this, I have two favorite options. The simplest is to change a waveform’s duty cycle (e.g., changing a sawtooth wave into more of a triangle wave) during the sustain. While this isn’t exactly how a guitar sounds, the effect can add interest.
The other option takes more work. With most of my lead guitar note samples, I create a layer with a sine wave an octave or octave + fifth above the fundamental to simulate the "whine" that feedback produces. This gets tied to mod wheel (or footpedal) so that increasing the mod wheel adds in the pseudo-feedback. Do this toward the tail end of a note’s sustain.
I’ve also experimented with using aftertouch to bring in feedback or add pitch bend, but satisfying results depend on the resolution of the aftertouch (you need real aftertouch, not "afterswitch" that feels like it’s either on or off) and the parameter being controlled. Any "stair-stepping" sounds pretty bad, but if the aftertouch is smooth, this can work well.
Sometimes a guitar sound depends on effects (chorus, flanger, etc.). However, the main "effect" is an amp that creates distortion, and a speaker cabinet, which is actually a very complex filter. Running your synth through a guitar amp is one possibility, but there are some great guitar amp simulator plug-ins such as IK Multimedia AmpliTube 2, iZotope Trash, Native Instruments Guitar Rig 2, Waves GTR, Universal Audio Nigel, etc. Just add distortion and a 2 x 12 cabinet for an extra "guitaristic" element.
Sure, you’ll get more authentic results with a Real Guitarist … but not always better results. Even though I play guitar, sometimes I break out a synth or sampler to do a "guitar" part because it has more of the vibe I want for a particular tune. Besides, it’s fun!