PLUCKING STRINGS

[Jim Coleman, Sr.]

Hi James:

I had just answered this question for someone else recently. Here is the
reason the pitch shows lower on your SAT when you pluck the strings. A 
hammerblow usually causes a wider amplitude (i.e. string movement up and 
down). As a string is hit by the hammer, a slight bit of increase in the
string's tension occurs. The higher tension increases the pitch so that
the early part of the sound will show the LEDs drifting to the right. When
a string is plucked, there is not as much amplitude and therefore not as
much increase in tension, so the pitch is indicated as being lower. I had
explained earlier that I like to tune with a hard blow so that there is 
just a slight drifting of the display toward the sharp side so that when
I play the key softly, the display will be stationary. This helps me get
greater accuracy when I watch for the display of the softer second key
stroke. In the high treble plucking is OK, however, the string will not 
be as well settled until a heavy keyblow is used. Therefore, pluck tuning 
only will leave a piano tuning very unstable or unsettled.

Another interesting thing about plucking strings is that if you pluck
in one direction, you may get one pitch indication, and plucking in
a different direction can give you a different pitch indication. This is
especially true when you have a wild string. The string may terminate at
the bridge pin when the vibration plane is in one direction while when
the vibrational plane is in a different direction and the termination
is at the wood of the bridge out in front of the bridge pin, the string
is essentially shorter in vibration length. This is the cause of much
of the beating in piano strings. You can prove this to yourself by removing
a string and noticing that the string groove in the top of the bridge 
extends out beyond the centerline of the bridge pins.

I have looked at vibrational patterns of strings using strobe lights, and
the oscillating back and forth of the vibration plane over perhaps a 5 
degree angle can clearly be seen. Now, when you pluck a string from the left
side, you get a different pitch than when you pluck the string from the
right side.

Jim Coleman, Sr.

On Sat, 28 Aug 1999, Jim Dally wrote:

> Hello Jim:  When I pluck a note I notice that the SAT shows it a little =
> flat as compared to the striking result.  I wonder how I should =
> interpret this.  It is helpful for me to pluck the treble strings, =
> especially those with false beats.  Any thoughts will be most =
> appreciated.  Jim Dally
>