Okay, finally an example of pure synth being playing by the guitar. But there would be no way to really play Ex. 6 accurately without the help of rhythm-chopping plug-ins. Frankly, to my ears and from my experience trying, the current state of MIDI guitar is just not good enough to play rhythmically with a synth plug-in, particularly if you hope to capture all the funky note mutings and rhythmic scratches that help make rhythm guitar compelling. Perhaps it can be passable for simple rhythms, but generally, you cannot match what a good keyboard player can do rhythmically.

In Ex. 6, what I played on the guitar is pretty darn simple. I start with a basic single-note line and then go into some chords. But all I’m doing is holding chords for a half-note or full measure—the software is doing all the rest. MIDI Guitar is routed to a TAL Software’s excellent TAL-U-NO-LX synth, and then getting chopped up, gated, delayed, and panned by the super-cool Audio Damage BigSeq2 plug-in (Fig. 6). I could post my dry guitar track, but like the Great Oz, I’d rather just say, “Pay no attention to that man behind the curtain.”

Fig. 6

In this next example (Ex. 7), I play a melody in D minor and then at the end of the first phrase I hit a high D on the 1st string. This note is mapped to the channel “on” button of a synthesizer track in Ableton Live. Once you hit that note, the track is enabled. The channel has a scale plug-in before the synth set to harmonize all the notes I play up a third, but in the key of D natural minor/F major. I also bend notes here to illustrate MIDI Guitar’s very usable pitch-bend tracking.

Sequencing and Notation
If you are ivory-challenged, using the guitar as a MIDI controller in conjunction with sequencing software or notation software can be a godsend. With sequencing software, latency and tracking delay concerns can be overcome since you can quantize or manually align notes. With most notation software, such as Sibelius or Finale, you can either import a MIDI part, or in some cases play directly into the software. Of course, you have to understand notation because inevitably you’ll need to correct misinterpreted rhythms, simplify confusingly written rhythms, change enharmonic notes to ones that are easier to read, etc. But this isn’t unique to guitar—imported or played MIDI parts almost always require cleanup, regardless of what controller created the parts.

In this notation example (Ex. 8), you can hear the raw guitar track playing a relatively simple melody in A minor. The guitar was converted to MIDI with both MIDI Guitar and Ableton Live’s Convert Harmony to New MIDI Track function. The MIDI Guitar track was also copied and quantized. All three MIDI tracks were exported from Live as MIDI clips and imported into Overture notation software, which in my experience does as good a job at intelligently converting MIDI files to notation as any notation software.

While all three imports are in the ballpark, there are some problems (Fig. 7). First, the key signature was not automatically converted, so you need to know what key the clip is in. Second, the guitar should be written an octave higher than it sounds—standard practice for guitar notation. Third, the triplet in the second measure was not captured properly. And finally, the third measure came out differently in all the three imports, with the Ableton Convert to Harmony being the closest. The last staff shows the phrase more properly and legibly notated, which I did manually. With even simpler lines, however, the chances of accurate MIDI transcription are higher, but you always need to be vigilant that the conversion-to-notation process was done accurately and legibly.

Fig. 7

Using the guitar as a MIDI controller does have its pitfalls, but it can be an excellent creative and useful tool. As I’ve attempted to demonstrate with the examples in this article, you can use your guitar to trigger extra MIDI notes with arpeggiators or harmonizers, trigger effects, and play sounds that don’t have to be “normal” instruments or even synths. You can correct for MIDI tracking delay and overcome groove-busting lags by forcing sounds through synchronized gating effects. An added bonus is that you can use guitar to input MIDI for sequencing and notation, though some cleanup is usually required. Hopefully, these examples get your brain thinking about novel and cool ways to use MIDI with guitar. Surprises await.

Testing Latency

With Jam Origin’s MIDI Guitar 2, I measured overall latency (which includes tracking delay from pitch-to-MIDI conversion) using the following procedure:

  • Record a simple one-note-per-string phrase from my guitar into a looper pedal to ensure performance consistency. From low to high, the notes were Bb–Eb–Ab–Db–Gb–B on the 6th and 7th frets.
  • Route the looper pedal output to an input of the audio interface.
  • Route an output from the audio interface to a miked amp.
  • Route the microphone in front of amp speaker to second input on audio interface.

I then setup the following tracks in Ableton Live:

  • Guitar input with MIDI Guitar 2 as a plug-in
  • Guitar direct input
  • MIDI track with keyboard plug-in (preferably using a sound with a sharp attack) receiving MIDI signal from MIDI Guitar 2 plug-in
  • Miked amp track

Next, I’d play the looped phrase and simultaneously record direct guitar and miked amp synth signal. Once the parts were recorded, I would zoom in to tracks and measure the distance in milliseconds (ms) between the start of the direct guitar waveform and triggered synth signal.

I repeated the procedure above with various buffer settings, running MIDI Guitar 2 as both a plug-in and standalone app while switching between monophonic and polyphonic modes. With a sample rate of 44.1 kHz and a buffer setting of 64 samples, I measured the following average latencies between the onset of a note with direct guitar and miked synth through an amp while running MIDI Guitar 2 as a plug-in on a channel in Ableton Live:

Note (low to high, 6th and 7th frets) Latency (milliseconds)
Bb 38.0
Eb 35.5
Ab 30.0
Db 26.8
Gb 24.3
B 21.2

I repeated the identical tests in Reaper, another DAW, and it yielded similar results.

Switching between monophonic and polyphonic modes in MIDI Guitar had little effect, though monophonic tended to show 1 to 3 ms less tracking delay. Trying different soft synth plug-ins also had little effect on the measurements, with perhaps a 1 or 2 ms difference between different soft synths. Running MIDI Guitar 2 as a standalone app and inputting MIDI from its virtual MIDI out or IAC Bus had little effect on latency performance, although with my system CPU performance was improved and I could get away with lower buffer sizes while running MIDI Guitar 2 in standalone mode rather than as a plug-in. Interestingly, the difference in measured latency between a 32-sample buffer and a 256-sample buffer in standalone mode was not too dramatic, while the CPU benefits can be very tangible.

Bear in mind these measured latency values include a software offset to make sure that output and recorded audio are in sync. With the test system here—a MacBook Pro i5 2.9 GHz Intel Core i5 with 8 GB of RAM and a Zoom TAC-2 Thunderbolt audio interface running at 44.1 kHz—the software offset needed (as measured in Reaper) is 185 samples, or 4.2 ms. Also, it is worth noting that the recorded MIDI data (the output from MIDI Guitar) was approximately 1/2 to 2/3 the latency of the recorded synth audio and generally under 20 ms. This seems to indicate that MIDI Guitar is remarkably fast at pitch-to-MIDI conversion.