The Rite of Strings - EMusician

The Rite of Strings

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,
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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.

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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.

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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).

A String of Polyphonies

Digital audio sequencers such as Apple Logic, Steinberg Cubase, and Cakewalk Sonar favor multichannel MIDI tracks. On the plus side, it is absurdly simple to record the individual MIDI output of all six strings. Editing is equally simple, especially if you color code the note display of the piano-roll-style window by MIDI channel. That way, each color will also represent one of the six strings (see Fig. 3). However, creating elaborate multitimbral setups as described for DP can be a convoluted affair.

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FIG. 3: A single track in Steinberg Cubase SX3 can handle all six MIDI channels from your guitar. Fortunately, you can color code each MIDI channel and string in its Graphical Editor.

Setting up a multitimbral virtual synth is usually a relatively simple process; if your target instrument is not multitimbral, you can always load multiple instances of the instrument (if your processor is up to the task). With DP's multiple-track scheme, you simply instantiate a multitimbral synth and assign the desired patch or patches to successive tracks and MIDI channels. In Logic, for instance, you assign a Multitimbral Audio instrument to a track, and set the track's MIDI input to All. You can then assign the patch or patches for each MIDI channel on the synth's multitimbral setup. If you want to send your guitar's MIDI output to different virtual synths, assign the MIDI inputs of individual tracks to each string's designated MIDI channel; you can then use Logic's arpeggiators, transposition, and other MIDI processors for individual strings (for more information about string transposition, see the sidebar “Tuner Casserole”).

To further minimize glitching, it's often best to limit multitimbral synths to monophonic performance for each string and channel. That way, the synth is limited in note choices. As an additional benefit, the instrument is more effective for playing clear solo lines, because with a single-note priority for each string, each successive note on the same string will stop the previous note, just like a guitar. Consequently, you will avoid the tails of long envelopes bleeding into your next note when playing on the same string. Most multitimbral soft synths provide easy access to voice-allocation parameters in order to conserve CPU cycles, and you can usually save your setup as a multitimbral patch (see Fig. 4).

Cleanup on Track Three

Glitches recorded in sequencer tracks can pose a different set of problems. If you're recording tracks with a software synth, unwanted notes can eat up available polyphony when you most need to conserve processor overhead. If you decide to change patches, the unwanted notes could become audible again or create other playback problems. Fortunately, most modern-day sequencers offer a terrific set of tools to remove musical blemishes. For example, Sonar offers a Deglitch function that's set up to surgically remove any data you don't want to keep (see Fig. 5), and Digital Performer's Split Notes command permits the use of similar criteria for removing unwanted notes. It takes a bit of practice to figure out what doesn't belong, but I can completely clean up an entire performance in seconds with either of those programs. In DP, using an event resolution of 480 ticks to a quarter note, I can select all notes with a duration of less than 50 ticks for removal and be done with it. Likewise, you can set a range of Velocities, and the programs will dutifully remove anything less than your minimum amount. Either method works well, but I prefer to cull notes by duration, because I may accidentally play an intended note too softly.

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FIG. 4: Here is a multitimbral patch I created in Native Instruments Kontakt 2. Each part uses the same bass patch assigned to one of the six MIDI channels of the guitar, and each part is restricted to single-note polyphony. In addition to conserving CPU cycles, this setup helps the samples perform like a real bass, with successive notes on the same string cutting the previous note short.

Having established several ways to clean up and fix your playing before, during, and after the fact, let me remind you that MIDI can easily become a playground for the obsessive-compulsive, and too much cleanup and precision can result in sterile tracks. A tiny amount of unevenness and glitching is a very human thing. That is especially obvious (and a bit ironic) if you need to deliver sequenced guitar parts. I'll wager that if you listen to any of your favorite guitar hero's tracks in isolation, you'll find plenty of sonic warts. For that reason, leaving that ghosted note you accidentally brushed while changing chord positions can actually contribute to the realism in the track.

Sure, the sequencer will let you set uniform durations for all the notes you played; however, one of the beauties of playing guitar is that each vibrating string has an independent life span, and some strings will naturally fade to silence sooner than others. Even if you are not trying to capture a realistic performance from your MIDI guitar, unrelenting uniformity can be exhausting to the ear.

Extra Hands

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FIG. 5: Cakewalk Sonar 5.2''s Deglitch feature is specifically tailored to remove spurious notes from MIDI guitar tracks.

Some MIDI guitar controllers, such as Terratec's Axon AX 100 mkII, provide a wealth of built-in modulation controls that are ideal for animating virtual synthesizers. Software synthesizers make modulation especially easy with MIDI Learn features and automation capabilities that practically invite complex sonic motion. The Axon's modulation sources include fretboard position, picking distance between bridge and neck position, the Pickup Control Wheel, two footswitches, and two expression pedals. Roland's GR-20 and Yamaha's G50 are also viable contenders. However, if your MIDI guitar controller is a bit underimplemented in the controller department, you have other options.

One truly terrific aspect of synthesis that stems from its early days is the concept of modularity — linking components that shape the instrument's expressive capabilities. In that sense, your MIDI sequencer can become a powerful component of a synthesizer system without recording a single note. As I mentioned earlier, you can use your synth's real-time MIDI processing for a great number of tricks. In addition, you can record lots of other types of MIDI data and use your sequencer as an adjunct LFO, envelope generator, or some other modulation tool for live performance. Record whatever CC messages you need into your sequencer tracks, and just let your sequencer play them back during your performance. You can either create tempo-synced effects or, for less predictability, ignore the tempo completely and just let the sequencer run free as you play. Most modern sequencers offer lanes to edit and “paint” virtually any number of MIDI messages.

Using a guitar to play synthesizers has always been and may always be a more complicated craft than using keyboards. At last, however, with greatly improved tracking and response time, the rewards easily outweigh the effort. There has never been a better time to play MIDI guitar.

Marty Cutler coauthored MIDI for Guitarists (Music Sales) with guitarist and friend Bob Ward in 1988. MIDI guitar has come a long way since then.

STAY ON TRACK

Apart from playing technique, other factors govern your MIDI guitar rig's performance. Here's a short list to ensure that your guitar will track as accurately as possible. First and foremost: use a well-maintained guitar with true intonation and good frets. Avoid extremely low string action and extremely light strings. Keep your guitar in tune and change strings often; it's not easy for a MIDI converter to judge pitch correctly if your string is a few cents sharp or flat. Likewise, if dirt, grit, and wear are warping the shape of your strings, they just won't track properly. And when it comes to tracking, magnetic hexaphonic add-on pickups are very good, but guitars with built-in piezoelectric pickups have the edge. Crosstalk between pickup poles and adjusting and readjusting pickup height are no longer issues, and you just can't track any better than with strings sitting smack-dab on the pickup. Check out instruments from Brian Moore and Godin Guitars. If you want to add a piezoelectric system to an existing guitar, check out GraphTech and RMC Pickups.

Your MIDI converter's sensitivity settings can also help. For example, Terratec's Axon AX 100 mkII lets you set a global threshold so that lightly excited strings will not send MIDI notes. A relatively quick-and-dirty remedy for unintended MIDI data is to tweak your synthesizer's Velocity curve so that notes resulting from false triggers are inaudible. Generally speaking, glitches have lower Velocities than the notes you intentionally play, so setting a curve that requires a high-Velocity threshold to produce sound will suppress glitch notes.

TUNER CASSEROLE

Ever since the demise of Roland's GM-70, the ability to store customizable MIDI tunings has been missing from guitar-to-MIDI converters (with the exception of Yamaha's G10, which used a proprietary controller instead of a real guitar). With version 5.26 of the Terratec Axon's firmware, customizable tunings have returned, topping a list of improvements (as of this writing, the current firmware is 5.42). The Axon's editing software offers a drop-down list of alternate tunings you can load and store in a preset, and you can add your own custom tunings to the list.

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FIG. A: Phi Software Open Tuning 1.5.1 lets you transpose the MIDI output of individual MIDI guitar channels and perform a variety of MIDI mapping tricks.

For controllers without open-tuning capabilities, Mac OS X users can download Phi Software Open Tuning 1.5.1 (see Fig. A). As with the Axon, you can choose from a long list of presets or customize and store your own. You can easily map any MIDI guitar's individual string output to play standalone soft synths directly or synths loaded into sequencers with Apple's IAC bus. If you want to use your controller on a single MIDI channel, you can create tunings by assigning MIDI Note Numbers to transposition zones; that offers intriguing possibilities for other single-channel controllers such as keyboards and wind controllers. You can download a free trial copy or purchase a full working copy for $29 at www.open-tuning.com.

You have at least two ways to achieve alternate tunings in your sequencer software. As long as your guitar controller is transmitting on an individual-string-per-channel basis, you can map notes to a new note. MOTU Digital Performer — because of its channel-per-track setup — does this easily. Some tinkering with the MIDI-mapping features of other sequencers (such as Apple Logic's Environments window) can provide the same result. Naturally, most multitimbral soft synths provide a transposing capability for each part, so you can create alternate tunings if your sequencer doesn't offer real-time transposition.