Unison coupling

[Richard Moody]

Hi Jim, 
	Yes I agree TuneLab is "very sensitive to the change of
 pitch in respect to time"  It is very sensitive to ANY change of
pitch, compared to another, perhaps more so than the human ear can
detect.  
 I know this is true for a long ("dwell" or sustain?) time.  
	Here are some theoritical numbers. 
 If the read out is in cents then a change of 1 beat in 20secs  at
221 is .4 cents.          221.00 - 220.95 = .05 bps  or 5 beats per
hundred seconds or one beat in 
20 secs. 
	  If .4 cents seems like a lot, then at 441, one beat in 20
becomes .196 cents, 
and half of that in the 880 or C5 octave.  TuneLab can be shown to
react to .02cents at A440. That is about when the bars start to
move. This of course has to be done with a fixed pitch source, not
a piano string.  Once this is done with fixed pitch then the piano
string can be compared.  The motion of the bars give an immediate
indication of change.  If the motion of the bars is related to
cents it is different across the span of the piano at 1 beat per
second. If they (motion of bars) relate to actual frequency
differences they will move the same anywhere in the compas at 1
bps.   

 	As far as pitch change in a a short time I do not know how to
ascertain this, (execpt a momentary fluxuation of the movement of
the bars) 
or record this, let alone measure this.  (But I don't see short
time pitch changes important in music or tunings)    Now if the 5th
and
6th octaves indicate a greater change (in cents) than the 3 and 4
octaves that indeed would be interesting, since the cents diff get
less in the
higher octaves for the same beat frequency (rate).  So far I have
been with TuneLab mostly below A440 to F3.  Now I would like to go
up two octaves.  

	Regarding the short time change, if one plays a note, say A220 on
the piano and lets it sustain for 3 seconds, then play a loud 440,
if there is a "pitch increase" shouldn't you hear that in the beats
of the first half second?   Or is half a second to short to hear
the difference?  If so, what difference does pitch increase make in
tuning?---unless tuning machines are fooled by it?   Likewise if
the pitch drops in time, shouldn't that be able to be heard in
beats? Let a note sustain for 7 seconds, play a loud note an octave
above.  Shouldn't there be a beat if the first note has been
loosing pitch?  Again if it takes more than 7 seconds for this
pitch drop to show up then it is of little or no importance to
music or tuning.   
	---ri C'ent 



> From: Jim Coleman, Sr. <pianotoo@imap2.asu.edu>
> To: Richard Moody <remoody@midstatesd.net>
> Cc: pianotech@ptg.org
> Subject: Re: Unison coupling
> Date: Monday, January 24, 2000 9:29 PM
> 
> Hi Richard:
> 
> It is my experience that TuneLab is very sensitive to the change
of
> pitch in respect to time. This seems to be more so in the 5th and
6th
> octaves. Perhaps I should take some time and put some numbers to
this.
> 
> The RCT shows this also.
> 
> Jim Coleman, Sr.
> 
> On Sun, 23 Jan 2000, Richard Moody wrote:
> 
> > 
> > Ron wrote...  
> > > >> >>The frequency of vibrating piano strings is not stable,
but
> > > >tends to 
> > > >> >>lower as the string continues to sound.
> > 
> > ric wrote 
> > > >I would like to see a reference to support this.   
> > 
> > Ron ...... 
> > >Note the pitch in the first half second or so of the attack,
and
> > > the drop in pitch as the note continues to sound. 
> > 
> > ric...
> > I do not have a SAT.   If the SAT shows pitch in the first half
> > second  different from the pitch in the next 2 seconds and
> > different again from pitch in the next four seconds, that would
> > indeed be most interesting information.  
> > 
> >