http://lamkins-guitar.com/music/article/easy-midi-guitar
David Lamkins picked up his first guitar a long time ago. As best he can recall the year was 1967: the year of the Summer of Love. Four decades later David has conjured up an amalgam of folk, rock and jazz solo guitar music for the occasional intimate Portland audience.
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location: Portland, OR USA

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Easy MIDI guitar

MIDI guitar doesn't have to be complicated. If you can do without polyphony (i.e. simply capturing single-note lines), buy a Sonuus G2M at US$99. This is a tiny box that runs on a 9V battery. Plug your guitar into one end and your MIDI cable into the other. The G2M will work with any pickup; there's no need to modify your guitar.

Assuming you're going to send the MIDI to some kind of program on your computer, you'll also need a way to get the MIDI into your computer. There are a bunch of low-cost MIDI-to-USB converters on the market. I use an M-Audio MIDISport Uno (US$39).

With any pitch-to-MIDI converter, tracking accuracy is "simply" a matter of playing clean - very clean - notes. All the little string noises and other sonic "embellishments" that make a guitar sound like a guitar become just another signal to the converter, which tries to assign a pitch and velocity to every noise - musical or otherwise.

Every player and guitar is a bit different, so you'll have to figure this out pretty much on your own. My own achilles heel was the end of the note. I'd lift my fretting finger while the note was still ringing. That caused the note to drop in pitch as the string came off the fret. Because of the damping of the fretting finger, you'd never notice that trailing artifact while playing. But the converter picks it up. I've learned to very carefully (and quickly) mute the note before moving my fretting finger.

BTW, when you get into this you'll encounter a lot of advice to adjust your guitar's tone and volume settings in certain ways to improve tracking accuracy. Ignore that advice. There's no "trick" to making a pitch-to-MIDI converter work well. It's all in how you play the notes.

You'll find the converter's tendency to glitch very frustrating at first, but you can - with practice - learn to play in a manner that gives you reasonably accurate tracking. Plan on spending some time playing the converter into a MIDI sound module for a while just to discover the proper technique. If you start out by plugging into a program that'll transcribe your playing, you'll be very disappointed. You really need to develop your "MIDI technique" first.

You'll also discover that there's a bit of latency between playing a note and getting the MIDI output from the converter. This latency is larger for lower notes. This is simply the way pitch detection works. It takes longer for the hardware/firmware to determine the pitch of a lower-frequency note.

Quantization is a function of the program you use to do the transcription. And, yes, they all provide a way to set up quantization. Even with quantization, don't expect perfect results. You will almost always need to do some manual editing after you record a line. Even so, I think you come out ahead unless you're really good at manual transcription (in which case, you probably wouldn't be interested in pitch-to-MIDI conversion for this application).

November 29 2010 03:39:21 GMT