INDIAN MUSIC FORUM ARCHIVES: Sitar Forum: string tension on indian instruments

 

Author Message
Stefan
string tension on indian instruments Jun 14, 2002 04:59 a.m.


Hello,

I am an amateur lute and guitar player
interested in indian classical music and
instruments.

I am looking for informations on string
tension on indian string instruments,
mainly for sitar, sarod, tanpura.

For instant, on a sitar the string tension
of the playing strings can't be to high
because pulling the string to the side
even further increases the tension
extremely (?)

Does anybody have informations on this?
Alternativley: What are typical combinations
of string length, diameter and material on
those instruments?

Greetings,
Stefan

Remco
Re:string tension on indian instruments Jun 14, 2002 12:20 p.m.


I think that it's a combination of many aspects. Indeed the meend technique (pulling) will dictate a certain string tension, but also the way the bridge is constructed, so it will give this resonating quality. If the tension is too low the strings will flop around and too tight they won't resonate. Listen for intance to a surbahar or veena. These instruments have an extremly long sustain, but have thicker strings than say a sitar...

peace,

Remco

K.K.
Re:string tension on indian instruments Jun 14, 2002 03:42 p.m.


Hi Stefan:
There's some pretty good info on string sizes, etc. at: www.silverbushmusic.com and www.fortepiano.com
Cheers
Stefan
Re:string tension on indian instruments Jun 17, 2002 07:58 a.m.


Hi Remco and K.K.

Thank you both for your replies.

Remco, I agree, that the string tension
depends on a lot of factors, as you
mentioned. I was just especially curious
about the meend technique. As a physicist,
I like to calculate things and I
found that if a sitar player pulls a string
to increase the tone by one fifths this
will more than double the string tension!
So I asumed initial string tension must be
lower than on the instruments I play
(guitar,lute), otherwise I can only pity
the poor sitar player's hand. (I have read
somewhere, that sitar player's can play a
fifths on one fret, perhaps this is wrong)

K.K., thanks a lot for your two links. They
are indeed good sources for information
on strings!

Greetings,
Stefan

Remco
Re:string tension on indian instruments Jun 17, 2002 01:50 p.m.


It's indeed possible to bend the string over big intervals. Funny thing: I heard a very large interval on a CD and told my teacher it must be a trick or something (this was after about 3 lessons: a meend from one whole step REALLY hurt my fingers) She looked at me like "What a wimp"and played a meend with those intervals. I'm a tall guy (6 foot 6) and she is this delicate little Indian lady!!! Very funny!!!
K.K.
Re:string tension on indian instruments Jun 17, 2002 03:01 p.m.


Stephan: If the sitar�s chicari posts and bridge are positioned correctly, you should be able to achieve AT LEAST a five-step meend, assuming it�s a quality instrument, of course.
Stefan
Re:string tension on indian instruments Jun 24, 2002 06:48 a.m.


Dear Remco and K.K.,

thank you for your clarification on
meend on the sitar. I was not sure
about these large intervals, because
to me it seemed to be too demanding
for the left hand fingers.

Greetings,
Stefan

Russ
Re:string tension on indian instruments Jun 24, 2002 11:45 a.m.


Hi Stefan;
Got to thinking about this a bit and thought I'd reply. I play both guitar and sitar, and I regularly bend the first string (pa) on the sitar 5 whole steps (notes) with no problem. But there's no way you could do that on the high "E" string of a guitar. Even with "slinkies" (very thin gauge), it would break if bent more than 4 steps (ouch!!). I believe the secret is not so much in the composition of the metal, but the string gauge and length. For example, a longer heavier gauge string with can take much more torsional stress before failing. Good example is a surbahar. Its strings can be bent one whole octave (8 whole steps) and not break!

Question for you. You mention that you found that the stress doubles for every fifth that's bent. How would that be determined if you don't know the original tensional stress? Just curious....

Stefan
Re:string tension on indian instruments Jun 25, 2002 04:45 a.m.


Hi Russ,

yes, string length and gauge are
surely very important for the
string's stability. I think the
crucial points here are the points
were the string is fixed at the
bridge and the nut. On a long
string instrument the side movement
of the string while pulling
is smaller compared to the string
length than on a short string
instrument. Thus the stress on
the fixing points is not so strong
and the string will last.

However, I still wonder about the
player's hands. I think it must
be a painfull experience to learn
playing the sitar in the beginning.


The calculation of the string tension
is as follows. The square of the
frequency of a string is proportional
to the string tension:

freq^2 = c*tension.

c is a constant that depends on the
string length, diameter and density.

If you use this equation for two
frequencies freq1,freq2 and the
corresponding tensions tension1,tension2
and divide the two equations this gives:

(freq2/freq1)^2 = tension2/tension1

The frequency of a fifths is 1.5 times
higher than that of the groundnote. Thus
in this case:

tension2/tension1 = 1.5^2 = 2.25
= more than doubled

For an octave on surbahar the
frequency is even twice as high, so
the tension2 is 2^2=4 times higher than
the initial tension1!

Greetings,
Stefan

Russ
Re:string tension on indian instruments Jun 25, 2002 10:43 a.m.


OK, I'm intrigued. Doing calculations is a part of my job as well, so I'm going to get a few numbers this week to throw into your formula and see what I get. Going to use actual frequencies, and going to use first string "cryowire" composition and standard diameter to determine the constant. Plus, I'm going to use the measured ratios of active string length (bridge to nut) to maximum side pull length for both a guitar and sitar. Anyway, I'll let you know what I come up with. I'm wondering about units. Is this dimensionless, psi or what is the unit or stress we're working with?

Yes, there is some pain involved with the tips of fingers when learning in the beginning, but because of this, callouses develop very quickly and the pain rapidly diminishes. But you'll find this experience, more or less, with any stringed instrument.
Stephen
Re:string tension on indian instruments Jun 25, 2002 11:04 a.m.


I would like to add a finding here that might prove helpful to someone in the future.
A few months ago I was scheduled to play at a wedding. At the time, my calouses had just over a year of development, thus no more pain.
Just two days before the wedding I end up with a cut just below my calouse's groove that was similar to a paper cut. No biggie until the sitar's string would find this new groove which felt like salt entering the wound. I was in a "no play" situation. The solution was a drop of super glue in the cut and 20 seconds later I was yanking on those strings. The cut never reopened and eventually the super glue surfaced and peeled away. It beats band aids.
Laughing Buddha
Re:string tension on indian instruments Jun 25, 2002 01:19 p.m.



Stefan (Jun 17, 2002 07:58 a.m.):
Hi Remco and K.K.

Thank you both for your replies.

Remco, I agree, that the string tension
depends on a lot of factors, as you
mentioned. I was just especially curious
about the meend technique. As a physicist,
I like to calculate things and I
found that if a sitar player pulls a string
to increase the tone by one fifths this
will more than double the string tension!
So I asumed initial string tension must be
lower than on the instruments I play
(guitar,lute), otherwise I can only pity
the poor sitar player's hand. (I have read
somewhere, that sitar player's can play a
fifths on one fret, perhaps this is wrong)

K.K., thanks a lot for your two links. They
are indeed good sources for information
on strings!

Greetings,
Stefan



This clearly shows what I always tell people about sitar.
If you want the tarbs to ring out clearly do a nice meend and they will.
One is putting so much more power into the system when the string is under tension like this and the result is that the whole body - and the tarbs - are pushed into resonating much more strongly.
Of course a good strong, determined, mezrab stroke also helps, except with cheap sitars with poor jawari which just choke when you do this hard picking..
I wonder if anyone has an equation for this? Power of meend and mezrab stroke - a challenge for someone? Lots of nice variables there.
Thomas Wanker
Re:string tension on indian instruments Jun 25, 2002 07:03 p.m.


Er uh, your equation is.......

E = MC2

Energy is equal to M (mizrab stroke force) x C (cuss words from cut on finger) x 2 (number of beers consumed in a rapid fashion).

Your very welcome.....know what I mean, know what I mean?

jerry
Re:string tension on indian instruments Jun 26, 2002 12:44 a.m.


Wow...
And I thought we were just playing music.
I got a grade C at school for Physics and I've carefully ensured that over the years I've erased from my mind what little I once knew.
Now I'm not sure I was right to do so.
Of course the Greeks considered music and mathematics to be branches of the same subject.
But they make dodgy kebabs so I never trusted them anyway...
K.K.
super glues Jun 25, 2002 07:42 p.m.


Hello Friends, FYI: Although it was used extensively during the Vietnam war for keeping troops from bleeding to death before they were able to get proper medical/surgical attention, it�s not recommend that cyanoacrylates (super glues) be applied directly to an open wound. The safest way to use �tissue adhesives� is to close the wound and apply the glue on the �seam.� This cuts down on the risk of infection and rejection. BTW, although it is classified/approved for human use in Europe and Canada, it�s not FDA approved. The best/safest glue available (in the US) is for veterinary use. You run the risk of toxicity problems with some of the over-the-counter stuff. Be safe � K.K.
Stefan
Re:string tension on indian instruments Jun 26, 2002 05:29 a.m.


Dear all,

Russ: I omitted the constant c because
it was not important for the above
calculations, but since you are going
to do your own calculations, here is
the complete formula:

freq^2=tension/(4*string_length^2*density)

string_length from bridge to nut. Density
is mass per volume of the string material.

The string tension is measured in any unit
of kind "force per area". I am familiar with
the metric system, so I would use
newtons/millimeter^2. psi should work too.
However, I don't how the "pounds" in psi
is defined (it should be a force unit) and
how it relates to the mass units. In any
case all units on the right side of the
equation must cancel out to give
Hertz^2=(1/s)^2, the unit of the left side.
You can use unit converter, to find relations
between different units, for instance:
http://www.pmel.org/unitconv.htm

I finally found the time to go trough the
recommended links, so can give an example.
According to the sitar tuning chart at
http://www.silverbushmusic.com/sitartuning.html
the highest playing string is tuned to Ma,
which corresponds to western f,
freq = 175 Hz
diameter = 0.012 inch = 0.3048 mm
I assume a string lenght of 0.9 m.
This might me completly wrong, I have never
seen a sitar close enough.
density = 7800 kg/m^3 (steel)

With these values I calculate

tension =4* (175 Hz)^2*(0.9m)^2*7800kg/m^3
= 773955000 Newton/m^2

Thus the force on the string would be
tension * area:

force = 773955000 Newton/m^3 * 3.14159 * (0.0003048 / 2)^2 m^2
= 56

10 Newton roughly correspond to the weight of 1 kg.

Thus, if the values I used a right, and you do
a 5 step meend (thus you double the tension), this is as if you were pulling on a string that is streched by more than a
10 kg weigth. Ouch!

Good luck with your calculations,
greetings,
Stefan

P.S.: sorry for this lengthy post

Russ
Re:string tension on indian instruments Jun 26, 2002 10:47 a.m.


KK- Thanks for pointing that out. I was going to say something but I didn't.

Jerry- Don't worry, this is just a sideline! Physics is not my bag either, although it is in my background. We are here for the music. But keep in mind that J.S. Bach used mathematical relationships between numbers to develop tempered tuning, the backbone of all western music. And hey, the Greeks do make a terrific gyro!

Stefan- Like Jerry said, wow! You've already got me scratching my head. But two things came to mind reading your results. First, I wouldn't use standard grade steel density for this one. I would use the body-centered crystalline, high temperature, high pressure, and high-carbon polymorph known in the materials trade as martinsite (type of cryowire, see the Silverbush description of this). Should yield significantly higher density. Secondly and more musically related, the force needed to play a clean note (or bend the note) increases as you move up the scale to the next higher note. Since I believe the frequencies (notes) are not fundamental integers of each other, the stress would increase by a log function. Therefore, it would be an upslope curve if you graphed frequency vs force, the curve being the constant of proportionality. A great deal more force is requied to pull a 5 note meend at the high C fret than is required at middle C. Don't need math to tell me that one as my fingers would do the talking (owwww)!

I also apologise for this long thread, but at least my bobbin is empty now. Sure wish the font size would quit doubling with each new paragraph. That's annoying!

K.K.
Re:string tension on indian instruments Jun 27, 2002 12:41 p.m.


Hey Jerry: What are "dodgy kebabs?" - K.K. (Kevin KARAMITROS)
jerry
Re:string tension on indian instruments Jun 27, 2002 01:01 p.m.


Hi KK
Speaking for myself of course, I love Greece. Did I mention how Mousaka is just my favourite dish? And that Plato, man he knew some stuff. I bet he'd even have understood this string tension thing.
It's London fast food joints that give kebabs a bad name IMHO. Next time we're both in Athens I'll buy you one.
Jerry
K.K.
Re:string tension on indian instruments Jun 27, 2002 06:39 p.m.


Jerry: Sounds good to me. I'll buy the first round of Ouzo! - K.K.
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