Unison coupling

[Jim Coleman, Sr.]

Hi Richard:

The change in pitch of the middle and low end of the piano is negligible 
in repect to time especially when you are listening to beats. However,
in the 5th and 6th octaves, one can hear the difference in the faster 
beating intervals such as 10ths etc. Play F3 and A5 together. Since the
F3 does not change much in respect to time, the slowing of the beat in
this interval of a 17th is due to the fact that the A5 is dropping in
pitch. This is easily seen on  the SAT, but you can also hear it. The
change is more rapid at first than later.

Jim Coleman, Sr.



On Wed, 26 Jan 2000, Richard Moody wrote:

> 
> 
> 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.  
> > > 
> > > 
> 
> 
>