I confess: I don’t like MIDI guitar. Or I didn’t. I guess what I don’t actually like is the accepted notion of MIDI (Musical Instrument Digital Interface) guitar, which is to turn our beloved 6-string into a controller to trigger cheesy synth sounds like pan flute, digital piano, or sampled sax. When you factor in tracking delays (the lag time between plucking a note on a guitar string and when a synth sound actually comes out of a speaker), note misfires, extra cables, special pickups, interfaces, extra floor pedals, and patching into a PA, the sonic promise of MIDI guitar seems musically questionable. In the past, I figured this technology was best left to YouTube noodle-nerds.

But on the other hand, I like effects. I like new sounds. I like trying to push sonic limits, especially since I get bored with stock guitar pretty easily. And though I can kind of get around on the keyboard, I have much greater facility on the guitar. So for sequencing or software-based notation, being able to just play guitar rather than hunt and peck on a keyboard would sure be nice.

After 30 years of MIDI guitar development, most guitarists now stay clear of using the guitar as a controller. Sure, MIDI is commonly used on floor controllers to change patches on multi-effect units or true-bypass pedal loopers, but this is different from using the guitar itself to play a synthesizer or control effect parameters.

We live in an incredible age of music software and synthesis, so it seems well worth taking a fresh look at MIDI guitar, especially in light of new ways to convert guitar notes to MIDI signals. And imagine the rewards if you could make MIDI work: You’d be able to tap into the vast galaxy of software synths and plug-in effects, create unique sounds, and input MIDI signals into sequencing software with ease. Rather than getting frustrated by the inherent quirks of using guitar as a MIDI controller, perhaps one can have a more Zen-like attitude. In this article, we’ll explore a bit of guitar synth history, the current state of MIDI guitar, and ways to take advantage of MIDI while minimizing the guitar-specific pitfalls.

A Brief History of Guitar Synthesizers
The early ’70s saw the introduction of guitar “synthesizers,” which were really analog effect units that created synth-like tones from a guitar pickup’s output while preserving the sound of a normal electric guitar. While these systems occasionally found users, few guitarists adopted them. They were expensive, unwieldy, and sonically limited or disappointing —especially when compared to a keyboard.

True guitar synths started to appear in the late ’70s. Rather than merely processing a guitar signal, these systems analyzed the pitches played on a guitar and then used the resulting information to control synthesizer circuitry. Roland developed a system that was widely adopted. They started with the GS500, followed by improved versions in the form of the GR300 and associated compatible guitars (G303 and G808). These guitar synths were polyphonic, had musically viable sounds, and delivered tracking speed and accuracy that some say has yet to be eclipsed.

While not perfect, these two systems offer a convenient—and thus very appealing—way to tap into the unlimited palettes of software synths and computer-based effects.

By the mid ’80s, MIDI had become established as a way of sending note on/off signals and other musical information from one device to another. Now there was a standardized way to control one synthesizer from a MIDI-compatible keyboard, or, as interest to us here, from a guitar equipped with a hexaphonic pickup and a pitch-to-MIDI conversion system. Roland, Ibanez, Charvel, and a host of other manufacturers offered pitch-to-MIDI conversion systems, with Roland’s GK hexaphonic pickups becoming the standard with their 24-pin (and later 13-pin) connection systems. In 1988, Casio introduced the MG-510 a Strat-style guitar with a built-in hexaphonic pickup, converter, and synth sounds.

Compared to the early Roland guitar synths, these MIDI-based guitar synths had latency issues—the time it takes between when a note is first plucked to when a synth sound is emitted. (For a detailed look at how I measure latency, check out the sidebar.) While keyboards have the advantage of directly triggering a MIDI note, a guitar has a vibrating string that needs to cycle around at least once before it can be recognized by the pitch-to-MIDI system as a musical note. For low notes, it can take over 10 milliseconds (ms) just for a cycle to complete itself, and longer for a note to stabilize and be a recognizable pitch. When combined with the delays inherent in the MIDI synths of the day, tracking delays of well over 50 ms for the guitar’s lowest notes were the rule. This is easily enough time to create a bothersome pause between physical action and hearing a sound.

To get around this tracking delay, a few manufacturers created guitar-like controllers that produced no sound on their own, like the SynthAxe and the Yamaha G10, but provided reduced tracking delays by bypassing the pitch-to-MIDI conversion process. While a few well-known guitarists like Allan Holdsworth and Lee Ritenour employed the SynthAxe, guitar-like controllers never gained traction in the broader guitar marketplace. Instead, the dominant MIDI guitar technology from the early ’90s to today remains a hexaphonic pickup driving a pitch-to-MIDI conversion circuit, sometimes built into a synth unit (like Roland’s series of rack and floor guitar synths, such as the currently produced GR-55).

In the last few years, there have been two notable advances in polyphonic MIDI guitar technology. The first is the Fishman TriplePlay guitar pickup, which transmits MIDI data wirelessly to a USB dongle for direct access to software synths and sequencing software. Tracking delays with the TriplePlay are dependent on software settings (sample rate and buffer size), but typical values for the Fishman TriplePlay seem to be comparable or perhaps slightly better than Roland’s current systems.

The second recent advance is Jam Origin’s MIDI Guitar software for computer or iOS devices, which requires no special pickup yet allows for polyphonic MIDI conversion. You connect your guitar to an audio interface, route it through MIDI Guitar, enable a software synth, and route out to a PA or amp. Measured tracking delays with MIDI Guitar software running as a VST plug-in within Ableton Live using a Zoom TAC-2 Thunderbolt audio interface set to a 44.1 kHz sample rate with a buffer setting of 64 samples, fell between about 30 ms for low notes and 20 ms for high notes.

While not perfect, these two systems offer a convenient—and thus very appealing—way to tap into the unlimited palettes of software synths and computer-based effects.

Setup
If you want to have a MIDI guitar setup that works in live situations, the first thing to consider is whether you want synth sounds to go to your amp or a PA. With a unit like the Roland GR-55 (which requires a divided pickup similar to the Roland GK-3), separate outputs are available for synth and guitar sounds. You can also route your standard, non-processed guitar signal to the synth outputs and send a blend of both signals to an amp or a PA.

With a laptop or tablet-based MIDI guitar synth setup, things can get a little more complicated. Fig. 1 is a diagram of one way to set things up.


Fig. 1

The limitation of the setup in Fig. 1 is that you can’t route computer-based effects or synth sounds to your amp. Fig. 2 shows an alternative setup that will route laptop-based synth sounds or processed guitar to your amp.


Fig. 2

With this second setup, the laptop essentially becomes an effects unit placed in a true bypass loop. It’s easy to switch the laptop in and out by simply hitting one button. With this approach, you need at least three separate output channels on your interface, or if you’re using a Mac, you can create an aggregate device in the Audio MIDI Setup utility to combine the interface and built-in outputs. With an aggregate device, you can run the Mac’s stereo outs to a PA system and your guitar from a mono output on your interface back into the true bypass looper. You select the channels on which to route guitar or synth sounds via software.


Fig. 3

Take a look at Fig. 3 to see how I’d set this up in Ableton Live. This screen shot shows Ableton Live running Jam Origin’s MIDI Guitar as a plug-in in the configuration illustrated in Fig. 2. Notice that the 2nd and 4th tracks are routed to output 3 (guitar amp) and the synth is routed to the master output stereo channels 1 and 2 (PA).