The EM Poll

The Rite of Strings

Jan 1, 2007 12:00 PM, By Marty Cutler

           

It's quite an awe-inspiring experience to pick up a guitar and play sounds that could never come from a guitar alone. The convergence of guitar, synthesizer, and MIDI promises new dimensions of creative expression and beautiful sonic complexity. Surprisingly, many guitarists with chops and credentials far better than mine admit to abandoning guitar synthesis in frustration, often with the complaint that the technology doesn't live up to its claims of accuracy, speed, and expressiveness. Their frustration often arises from a lack of understanding about synthesis and MIDI. To paraphrase a well-known comic strip, “Music technology is not for wimps.” That said, it has never been easier to gain control over a vast array of synthesizers, sequencers, effects, and other MIDI technology that can take your music and creativity to unexpected places. MIDI guitar converters track better than ever and offer as much if not more expression than the average keyboard.

What follows is a grab bag of tips and advice for anyone contemplating the merger of guitar and synthesizer, and for the seasoned pro in search of new ideas. To skilled keyboardists and synthesists, some of my advice may seem obvious, but remember that I am approaching synthesis from a guitarist's point of view. Nonetheless, keyboardists can glean useful information about guitar techniques as they apply to MIDI and synthesis. (For more information, check out “Six-String Synthesis” in the May 2002 issue of EM, available online at www.emusician.com.)

Gater Aid

It's helpful to examine the fundamental differences between the ways that keyboards and guitars trigger MIDI data. MIDI keyboards are essentially a series of switches. Press a key, and the keyboard will generate MIDI Note On and Velocity messages; release the key, and it will generate a Note Off message.

Guitars, however, go through a more complex process in order to generate MIDI notes. First, a converter needs to translate a vibrating string into MIDI data (for more details on the process, see “The World on a String” in the May 2001 issue of EM, available online at www.emusician.com). Guitar techniques can confound the unambiguous language of MIDI protocol. MIDI guitars send note data for as long as the converter can sense the vibration of the strings; consequently, some strings (usually the lower-pitched ones) may vibrate longer than you want them to, or they may ring for a shorter time than you intend. Some guitarists lift their fingers from the strings in order to damp notes, and the fretting hand moves around when changing fingering positions. Either action can inadvertently set strings into motion and trigger additional MIDI notes. Not to put too fine a point on the comparison, but unless you are incredibly clumsy, lifting a finger from your keyboard's middle C will not accidentally trigger other notes.

FIG. 1: Although this Subtractor patch in Propellerhead Reason 3.0 has a slow attack, you can set the Amplitude Attack knob in the Velocity section’s lower-right corner to speed up the envelope’s attack segment with higher Velocities.

Guitarists have developed a wealth of techniques for controlling their instruments, and I have found it most useful to borrow from the pedal steel guitarist's bag of tricks. The pedal steel can be characterized by its languid, rich sustain and often slow, violin-like attack. Nevertheless, masters of the instrument can fire off intricate bebop solos and seamlessly switch to gorgeous, sustained padding without changing any instrument settings. It's all in the picking hand, and one technique (often called blocking) translates quite well to MIDI guitar.

All nonessential picking fingers remain relaxed but curled under the palm of the hand. You damp notes (and consequently send MIDI Note Off messages) by rocking your picking hand as you play so that you damp the strings with the meaty edge of the palm near the base of your pinkie at some rhythmically appropriate point. You can also alternate the pinkie edge with the thumbside edge of your palm. The technique takes a bit of practice to perfect, but it works well whether you use a flat pick, fingerpicks, bare fingers, or any combination. As you develop more coordination in the technique, work on changing chord positions while the notes are damped to minimize false triggers. (For more tips on how to maximize tracking, see the sidebar “Stay on Track.”)

Envelopes Rule

One of the most frequently mentioned concerns of MIDI guitarists is that the synthesizer doesn't respond quickly enough for rapid note passages. Most often, delays can be attributed to the guitarist attempting to play the head of a Mahavishnu Orchestra tune with a tuba patch or some other sound that has an inappropriately slow attack. Stop and think for a moment: how many tuba players can negotiate the passage in question without risking a hernia? MIDI guitar is not at fault here; keyboardists attempting that same passage with the same patch would face the same problem. Synthesizers take on certain sonic properties only if they are programmed that way. Thus, sounds with a slow attack segment will repeat that behavior with each note, and no rapid-fire barrage of 64th-note triplets is going to make them more responsive.

To achieve more-satisfactory results, you have several options: play fewer notes (almost always good advice), choose another sound, or tailor the one you're playing to suit your style. It isn't hard to adapt a synthesizer program to your playing needs, but be aware of a significant catch-22: adjusting the sound may obscure or even eliminate some of the characteristics that attracted you to it in the first place. For example, speeding up the attack of a slowly evolving pad sacrifices motion for a faster response. The best option here is to choose an instrument that lets you control envelope rates with picking dynamics (Velocity). If you play softer, the attack remains slow, but with more forceful picking, it speeds up (see Fig. 1). If you have a spare oscillator, you might be able to add an attack transient that gets out of the way quickly. Of course, you could always blend your guitar's output with the synth too.

Please Release Me

The release stage of the envelope can also create problems when you want to play faster passages: if one note doesn't get out of the way of the next note soon enough, the performance can be garbled, with the tails of notes slowly receding into silence. Remember: the programmed release stage of the envelope supersedes the physical release of the string; therefore, in order to avoid smearing the part, simply abbreviate the release stage of the patch.

Of course, nothing is better for sequencing realistic acoustic guitar parts than a guitar controller, but if you need to sequence guitar parts, avoid patches that use sampled string-noise artifacts in release loops unless you can invoke them with a Control Change (CC) message. While you are trying to lay down a part, nothing is more confounding or annoying than fret noise and string snaps automatically popping up — it's often hard to tell them apart from a bad case of glitching. If you want to add playing artifacts for realism, it's best to invoke them with CCs after laying down the track.

If Six Were One

It's hard to explain the particular appeal of monophonic lead instruments, but even the most powerful, high-end synths with oodles of polyphony feature sounds that restrict playing to monophonic lines. The sustain of the synth, coupled with a gliding, legato behavior, seems to encourage wide intervallic leaps and more hornlike phrasing than if you were simply playing guitar or a polyphonic synth. It's very different from playing monophonic lines on guitar and requires a few modified techniques, but trust me, it opens up plenty of new ideas for expression. The trick is to use a subtle amount of the synthesizer's glide (or portamento) to create smooth and continuous transitions from note to note without any semitone stops at intermediate frets.

Here again, you need to be aware of the way the synthesizer is programmed; for example, you might want to speed up the portamento time so that gliding from one pitch to another doesn't sound too exaggerated. If more than one note is ringing, the synth may glide to a different note than you intended, depending on whether the monophonic patch is set for low-note or high-note priority. Consequently, some of the previously mentioned blocking techniques can ensure that sustained notes don't glide to the pitch of another string that may still be vibrating.

FIG. 2: MOTU Digital Performer’s Sequence Editor lets you combine and edit multiple tracks as if it were a single Graphical Editor window.

Guitar Meets Sequencer

Recording MIDI guitar tracks into a software sequencer requires a bit more forethought than the average keyboardist needs to confront. First, you must determine if you will record MIDI data over a single MIDI channel or use one channel per string. You have many more options if each string's output has a dedicated MIDI channel, but that requires advance setup in the guitar controller as well as the host program. Most obviously, you will need to consider the way in which the sequencer handles multiple MIDI channels. If you are using software synthesizers, you'll have to think about setting them up for multitimbral performance.

For the MIDI guitarist, there are two basic ways a sequencer can handle multiple-channel recording of MIDI data; both approaches have their pros and cons. MOTU Digital Performer (DP), for example, operates on a single-MIDI-channel-per-track basis. That means you will need to set up six tracks, one for each string and its associated MIDI channel. Although it may seem a bit unwieldy from a visual standpoint, there is a major advantage to this type of setup: you can use DP's real-time MIDI Effects plug-ins to easily transform your MIDI guitar input in a variety of flexible ways. You can quickly transpose any individual string and simultaneously harmonize it to virtually any imaginable scale while applying a customizable arpeggiator. You can create polyrhythmic, multitimbral monsters. Furthermore, DP's Device feature lets you stack synths, so each string could have custom synthesizer layers. Of course, multiple tracks can be difficult to manage if you are cleaning up glitches or fine-tuning note durations. Fortunately, with the advent of the Sequence Editor window, DP lets you view multiple tracks in a unified piano-roll-style editor (see Fig. 2).