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The
following is the first part of the content discussed at my MIDIGuitar clinics.
What is a MIDIGuitar System
To answer that I'll have to explain what MIDI is first.
OK, So What is MIDI?
MIDI is the language that lets digital musical instruments talk to each other.
Originally developed to allow different keyboard synthesizers to play each others sounds,
it has grown to the point where virtually every high tech musical device has some sort of
MIDI control. It has been the method of choice for controlling and switching synths,
effects, amps and even lighting systems for years.
So Now: What Is MIDIGuitar System?
A MIDIGuitar system is a system which allows you to control MIDI devices such as
synthesizers, samplers and sound modules using a guitar as the controller instead of the
more common keyboard. While they are sometimes called guitar synthesizers, this actually
only describes a smaller number of systems which have both the guitar to MIDI converter
and a built-in sound source such as a synthesizer.
MIDIGuitar Hardware
Requirements for MIDI Guitar?
- Guitar - This should be self-explanatory, but you never
know...
- A Hex Pickup - A pickup with 6 pickups in one package. There
is a separate pickup for each string (we'll see why just now)
- A Guitar Synthesizer OR
- Guitar to MIDI converter and separate sound source.
Hex Pickups:
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Roland GK-2AH
(External Electromagnetic) |
Roland GK-KIT-GT
(Internal Electromagnetic) |
Graph Tech Ghost saddles
(Internal Piezo) |
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External Electromagnetic -
Such as the Roland GK2-AH. These are the most common and attach externally to any
steel-strung guitar. Consist of six small electromagnetic pickups in one package and a
separate box with controls and sockets. PROS: No permanent modification of guitar
required. CONS: Unattractive (unless you have a Borg fetish), Only work on steel-strung
guitars, needs to be well positioned. Internal
Electromagnetic - Such as Roland GK-KIT-GT. The same as the external, but made to fit
much of the electronics inside an electric guitar. PROS: Less obtrusive than external
versions. CONS: Pickup still visible, Only for electric guitars, also needs to be well
positioned.
Internal Piezo - Such as Graph Tech Ghost. Pickups
are built into saddle of guitar, electronics are internal. PROS: Unobtrusive, also give a
useable acoustic sounding piezo output, models available for all types of guitar - even
nylon. CONS: Require guitar modification.
Pre-Installed Hex Pickups
Some major manufacturers such as Fender, Brian Moore and Parker are manufacturing
guitars with hex pickup systems built in. These are often called "Roland-Ready".
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Roland Ready Stratocaster with GK-KIT-GT built in |
Guitar to MIDI Converters
e.g. Roland GI-20, Axon AX-100, Roland GR-33. This is the main componant
of a MIDIGuitar system. Takes the hex signals and carries out pitch recognition,
converting to MIDI notes. Outputs a concentional MIDI signal - playable by any MIDI
capable synthesizer. Due to the fact that the note must sound first before it can be
recognised and converted, there is always a short delay - especially noticable on the
lower notes.
Synthesizers
e.g. Roland XV-2020 or XV-5050. Self-expanatory. These are the sound generating
portion of the system, and can be samplers, synthesizers, software synthesizers,etc.
Combined units
e.g. Roland GR-33. These combine the guitar to MIDI convertor and a
synthesizer in one package. Are convenient (especially for gigging) but limited
sound-wise.
Optimum MIDIGuitar Setup
Due to the nature of the conversion process, MIDIGuitar
is prone to "glitching" (playing the wrong note or appreciable delays before the
note sounds). This is mostly due to the convertor trying to recognise sloppy playing
technique and struggling with spurious noises such as string squeaks, fret buzzes and
crosstalk between strings (where the pickup for one string will hear the two strings next
to it).
To Minimise glitching, it is essential that the guitar be
set up as well as possible with no string buzz or rattles. Clean, clear tone equals clean,
clear conversion to midi. The better the guitar, the better the performance.
In the case of electromagnetic hex pickups, the pickup must
be as close as possible to the bridge, where the notes fundamental is strongest and
overtones are minimal. Must also be within 1-2mm of the strings. This helps minimise
crosstalk.
Intonation must be as accurate as possible, as this aids the
pitch recognition. Also when playing blended sounds with both a guitar sound and a synth
playing they might be out of tune with each other.
Playing Problems
What is Tracking?
Tracking is the speed and accuracy with which a guitar-to-midi converter
interprets the analog signal and converts it to a MIDI note. Basically means how much of a
delay is between the note you hear from the guitar and the note you hear from the synth
and whether that note is the correct one or not.
Playing Technique
This is where most new MIDI guitarists have problems. You may think you are an
accurate, clean player, but until you have played a MIDIguitar, you have no real idea. The
system will expose every weakness in your playing and make it more apparent as it
glitches. Be prepared to spend time learning how to modify your playing technique to
eliminate problems.
It is also important to note that some guitar technique does
not readily translate to some synthesised sounds - a piano sound will sound silly when
strummed. Also, bends are not usually part of a pianist's arsenal of techniques.
Guitar to MIDI Convertor Setup
It is essential that your convertor is set up to respond well
to your playing. While there are no exact setting that will work well for everyone, some
tweaking is in order, namely:
MONO Mode vs. POLY Mode
Mono mode is where each string has it's own MIDI channel. This lets you do nifty
things like have a different instrument on each string. More importantly, the convertor
can follow what you are doing better if it knows there can only be one note at a time on
each string - if it thinks it hears two notes, it listens again and checks.
Poly Mode is where all 6 strings play one MIDI channel, which used to be handy with
older convertors and synths, where you would start running out of channels when you had
too many layered sounds at once. Has little relevance with modern systems.
String Balance
Not every string on a guitar is the same volume. While this is part of the
character of the instrument we love and we expect to hear that variation, it can become
obvious and annoying with a synth sound. All Guitar-MIDI convertors have the facility to
set the relative levels of individual strings, allowing you to balance the levels.The
Roland GI-20 even has the option to save settings for four different Guitars!
Sensitivity Settings
Think about the difference in volume between your soft fingerpicking and your
loudest "balls to the wall" playing - quite a difference in levels! Some synth
sounds may respond better to a particular level, particularly those which have a velocity
cross switch - where the sound will change from one tone to another, depending on the
velocity played. Sensitivity allows you to set a patch so that it responds to your soft
playing as if you were playing a lot harder, and vice-versa.
Bend Ranges
Bend ranges specify how far a note can be bent. It is essential that the
bend ranges of your Convertor and your synth match. If one is set to 12 semitones and the
other two, the guitar sound and the synth sound will be out of tune with each other as you
bend. It also makes for unreliable tracking.
Also note that if you do not need to bend in a particular
patch, set your bend range on the convertor to 0 (or 'chromatic'). This produces a lot
less MIDI information and makes the tracking a lot more stable and glitchfree. |
