[sdiy] pitch tracking / guitar synths

[harrybissell]

inline...

WeAreAs1 at aol.com wrote:

>> As for cleaning up the guitar signal the GR-300 uses a tracking
>> filter
>
> Hello Dave,
>
> I think you're mistaken about there being a tracking filter in the
> GR-300.  The circuit for each string has a separate fixed-frequency
> filter which attempts to limit to response of that string channel to
> just the two octaves (or so) that the string produces.  They made no
> attempt to have the filter frequency track the string frequency.

well I guess "Certs" is a "candy mint" ~and~ a "breath mint".

The tracking filter... is not a fixed filter.  It is an adaptive
bandpass filter that
changes its er... bandwidth (for want of a better term) depending on its
estimate
of whether you are playing above, or below... the fifth fret of that
string. For the
lower notes its stacks the two bandpass filters for much more harmonic
rejection...
and higher notes it widens the bandwitdh to include the 12th fret. If
you play the
twelfth fret and then pull off to the open E... bets are it will keep
playing the
high E because the filter was open and includes the harmonic.  Still...
its a good
choice.

> It would sure be nice if the GR-300's audio filter actually did track
> the note you were playing (I'm talking about the resonant filter that
> you can hear and adjust, not the fixed ones that help the P/V
> converter do its job).  You kind of have keep adjusting and fiddling
> with the filter cutoff frequency as you play up and down the neck.
> Otherwise, your sound is alternately too buzzy (for low notes) or too
> muted (for high ones).  Unfortunately, the GR only has one master
> filter which filters all six strings simultaneously (kind of like a
> Korg Poly800 or an ARP Omni), so it would be pointless for them to
> have that filter try track your playing.  I guess what I really wish
> for is a separate tracking filter on each string.
>
>
Be careful what you wish for... The problem is that Roland really
avoided doing anything with the
pitch 'voltage'  This is the right move imho. There is so much chance of
getting a
wrong voltage and blowing the filter WAY off course. With high resonance
it could be
a disaster.

A better choice might be a filter per string, but a 12dB one. That would
stop a lot of the
timbre difference and still allow dynamic changes. But IF you had a
filter per string...
what would you control it with ? Envelope follower per string ?? ADSR
per string ???

ADSR would not work, because the "R" is instant. The signal will be gone
before the
filter can close (unless you are sustaining it a long time).  Triggering
might be erratic
as well.

I don't even remember if they offset the filter for each string you play
on. That might
get abrupt in tone color as well.

It was a good early attempt at full polyphony.

H^) harry