Guitar synths

[Scott Gravenhorst]

Another interesting technique is the way the Roland GR-50 works.

When a string is plucked, the synth electronics measures the rise time
of the first quarter of a cycle.  This value is used to set the pitch
of the attack portion of the note which is initiated at that time, which
is only one quarter of a cycle late.  The attack pitch is often not exact, 
but within a full tone usually.  A frequency counter of sorts is also 
monitoring the string.  Once the freq counter stabilizes, the synth pitch 
is adjusted to accurately match that of the vibrating string.  This 
usually occurs before the attack portion is finished.  
So this technique is nearly immediate, and since the pitch error occurs
during and is corrected during the attack phase, it is pretty well masked,
especially if a percussive attack sound is used.

For a guitar that is strung normally, string 6 has audible MIDI delay.
This can be reduced by using a nonstandard stringing.  I use strings
that are 1/2 the normal diameter for strings 5 and 6, and I tune those
up an octave.  This preserves the fingering and improves the synth's
response time for both MIDI and the internal sounds.  It actually sounds
pretty cool tuned like this.  However, like other's have noted, using
this instrument to drive external sound modules is not very good unless
a slow attack pad-like sound is used along with the natural sound of the
guitar.  The fact that the GR-50 is really a D-110 means that those
pads are already available as internal sounds, so using MIDI really
isn't worth it.

Don T. mentioned another Roland g-synth that uses a distorted version of
the vibrating string as the attack sound and then switches over to
a VCO once it has "found" the correct pitch.  PLLs might be cool to
use here, since they can multiply frequency.  

-- Scott Gravenhorst
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