RMIM Archive Article "330".
From the RMIM Article Archive maintained by Satish Subramanian
#
# RMIM/C Archives..
# Subject: Tanpura - C V Raman's paper
#
# Posted by: Rajan Parrikar parrikar@rococo.colorado.edu
# Author: C V Raman
#
Namashkar.
The following is the text of the original paper on the acoustic
properties of the tAnpurA authored by Pandit C.V. Raman (I apologize
very deeply to this newsgroup for using for the first time in its
history the "Pandit" title on someone truly deserving of it). Pandit
Raman won the Nobel Prize in Physics in 1930 and his family's
contributions to knowledge and civilization have been singular. His
brother, C.S. Ayyar, was an eminent musicologist (and a fairly
controversial figure in Carnatic circles). Ayyar's daughter, Vidya
Sankar, is an exceptional scholar-musician. And Ayyar's eldest son,
Pandit S. Chandrasekhar - scholar and mathematician extraordinaire -
did pioneering work in, among other areas, stellar structure for which
he was awarded the Nobel Prize in Physics in 1983. All this is of
course very well known to even pre-kindergarten level children in all
of India except bongland where they instead prefer to have zero
knowledge and infinite humility at all times (except for the brief
moment when they craft their resumes when both quantities assume the
value zero).
On the subject of musical acoustics, the indispensibility of Fourier
Methods as tools for analysis is today well-known. Not as well known
is that Fourier had trouble getting his ideas accepted when he first
presented them to the French Academy circa 1807. What is astonishing
is that the germ of an idea was not picked up by any of the three
mighty mathematical minds of France of the time - Pandit Laplace,
Pandit Legendre and Ustad Lagrange - and Fourier came in for some
stick at their hands. This seems surprising to us today, but the ideas
of convergence were not fully developed or appreciated at that time
and had to await another generation inaugurated by Pandit Cauchy.
Photocopies of this paper (and some other related ones) were excavated
and sent to me by Krishna Kunchithapadam of the University of
Wisconsin - Madison (krisna@cs.wisc.edu) soon after the thread on
Tanpura died some weeks ago on this group. Perhaps we will see a
resurrection. Since the paper has been scanned a few typos may yet be
alive.
I don't tune in so if someone wants a copy of the original (with
figures et al) send email to: parrikar@rococo.colorado.edu
Warm regards,
r
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>From: proceedings of the Indian Association for the Cultivation of
Science 7 29-33 (1921).
On some Indian stringed instruments
C V RAMAN, M.A., D.Sc. (Hon.)
(Palit Professor of Physics in the Calcutta University)
(Plate I)
CONTENTS
I. Introduction II. The form of the bridge in the "Tanpura" and the
"Veena" III. The failure of the Young-Helmholtz law IV. Outline of
mechanical theory V. Summary
1. Introduction
A fascinating field for research offers itself in the scientific study
of the numerous kinds of musical instruments to be found in
India. Some of these instruments of indigenous origin are of undoubted
antiquity and disclose a remarkable appreciation of acoustic
principles. An investigation of their special features in comparison
with those of instruments of other countries may be expected to yield
results of great interest. An instance of the fruitfulness of the line
of work here suggested is to be found in the present author's research
on the Indian Musical Drums, which have been found to embody in a
practical form the solution of the problem of loading a circular
drumhead in such a manner as to make it give a harmonic succession of
overtones in the same way as a stringed instrument (*). In the present
paper it is proposed to offer a preliminary note on the results of the
author's study of some Indian stringed instruments.
* See NATURE (London) 8 February 1920. A fuller account of the work on
these musical drums is shortly to be published as a Bulletin of this
Association.
2. The form of the bridge in the "Tanpura" and the "Veena"
The "Tanpura" and the "Veena"are two of the most highly valued
indigenous stringed instruments intended to be excited by
plucking. Plate I, figure 1 illustrates the form of the
"Tanpura". This instrument has no frets and is intended merely to be
used as a drone in accompaniment with vocal or other music. It has
four metal "strings" which are stretched over a large resonant body
and can be accurately tuned up to the right pitch by a simple device
for continuous adjustment of tension. The remarkable feature of the
"Tanpura" to which I wish to draw attention is the special form of
bridge fixed to the resonant body over which the strings pass. The
strings do not come clear off the edge of a sharp bridge as in
European stringed instruments, but pass over a curved wooden surface
fixed to body which forms the bridge. The exact length of the string
which actually touched the upper surface of the bridge is adjusted by
slipping in a woollen or silken thread of suitable thickness between
each string and the bridge below it and adjusting its position by
trial. Generally the thread is moved forwards or backwards to such a
position that the metal "string" just grazes the surface of the
bridge. The description will be clearer on a reference to figure 3
above where the bridge and the string passing over it are indicated
diagrammatically.
The "Veena" on the other hand is a fretted instrument intended for use
in playing melodies (figure 2 in plate 1). The form of the bridge
adopted in it differs from that of the "Tanpura" in two respects. The
upper curved surface of the bridge in the "Veena" is of metal and the
special mode of adjustment of contact by means of a thread used in the
"Tanpura" is dispensed with, and the string merely comes off the
curved upper surface of the bridge at a tangent, as indicated
diagrammatically in figure 4. (No attempt is made in this figure to
indicate the exact form of the lower part of the bridge).
The bridge of the "Veena" is also much higher above the body of the
instrument than in the "Tanpura". Even when the strings are pressed
down on the frets when the instrument is being played, the curvature
of the upper surface of the bridge ensures the string always leaving
the bridge at a tangent to it as shown.
3. The failure of the Young-Helmholtz law
The special form of bridge illustrated above has a very remarkable
influence on the tone-quality. This can be most readily demonstrated
in the "Tanpura". When the adjustment of contact of string and bridge
is made carefully by trial the instrument is highly sonorous, giving a
tone of fine musical quality. If on the other hand the grazing contact
of string and bridge is rendered inoperative (as for instance by
inserting a small piece of metal between the string and the surface of
the bridge) the tone becomes dull and insipid. A similar remark
applies also to the case of the "Veena," though the difference is less
striking in the latter case.
In attempting to find an explanation for the difference in
tone-quality produced by the special form of bridge, the author made a
surprising observation, namely, that in the tone ofthe "Tanpura" or
the "Veena," overtones may be heard powerfully which according to
known acoustical principles should have been entirely absent.
According to the law enunciated by Young and Helmholtz, if the string
is plucked at a point of aliquot division, the harmonics having a node
at the point of excitation should be entirely absent. This law may be
readily verified on an ordinary sonometer with the usual form of
bridge. For this purpose, the position of the node should first be
found exactly by trial by putting the finger in contact with the
string and plucking elsewhere so as to elicit the overtones
desired. Having found the position of the node, the string should be
plucked exactly at that point and then again touched with the finger
_at the same point_. On an ordinary sonometer, this results in the
sound being immediately quenched inasmuch as the finger damps out all
the partials except those having a node at the point touched, and the
latter are not excited in the first instance in accordance with the
Young-Helmholtz law. On trying the same experiment with the "Veena" or
the "Tanpura", it will be found that the overtone having a node at the
plucked point sings out powerfully. In fact the position of the
plucked point hardly appears to make a difference in regard to the
intensity of the overtones in the "Tanpura". This remarkable result is
not due to any indefiniteness in the position of the node point, as
the latter is found to be quite well defined as is shown by the fact
that in order to demonstrate the effect successfully, the string must
be plucked and then touched exactly at that right point, otherwise the
sound is quenched. We are thus forced to the conclusion that the
effect of the special form of bridge is completely to set aside the
validity of the Young-Helmholtz law and actually to manufacture a
powerful sequence of overtones including those which ought not to have
been elicited according to that law.
4. Outline of a mechanical theory
Some photographs of the vibration-curves of a "Tanpura" string were
made at the suggestion of the author by Mr Ahmed Shah Bukhari at the
Government College, Lahore, last November. They showed that in
consequence of the grazing contact at the bridge, the vibration of the
string decreased in amplitude and altered its form at a much more
rapid rate than when the grazing contact was considered ineffective. A
more complete investigation is obviously desirable. >From first
principles, however, it is obvious that in the "Tanpura" the forces
exerted by the vibrating string on the bridge must be very differnt
from what they would be for a bridge of ordinary form. It seems
probable that by far the greater portion of the communication of
energy to the bride occurs at or near the point of grazing
contact. The forces exerted by the string on the bridge near this
point are probably in the nature of impulses occurring once in each
vibration of the string. This would explain the powerful retinue of
overtones including even those absent initially in the vibration of
the string. At a slightly later stage the reaction of the bridge on
the string would result in a modification of the vibration form of the
latter and bring into existence partials absent initially in it. There
would in fact be a continual transformation of energy of vibration of
the fundamental vibration into the overtones.
The foregoing explanation of the character of the tones of the
"Tanpura" would not be fully applicable to the "Veena" as the forces
exerted by the string on the bridge in this case would not be purely
of an impulsive character. There is however a certain portion of the
bridge over which the string comes into intermittent contact during
the vibration, and it seems very probable that the theory for this
case is intermediate in character between that for the "Tanpura" and
those for stringed instruments with bridges of the ordinary
type. Further experimental work is needed in support of this view.
5. Summary
The present paper deals with the remarkable acoustic propertm of the
"Tanpura" and the "Veena" which are two of the most highly reputed
among Indian stringed instruments. The form of the bridge used in
these instruments is quite different from that usually found in
European stringed instruments. In the "Tanpura" the string passes over
the wooden upper surface of the bridge which is curved to shape, and
by insertion of a thread of wool or silk, a finely adjustable grazing
contact of string and bridge is secured. In the "Veena" the upper
surface of the bridge is of curved metal and the string leaves it at a
tangent. The tones of these instruments show a remarkable, powerful
series of overtones which gives them a bright and pleasing
quality. Experiment with these instruments shows that the validity of
the Young-Helmholtz law according to which partials having a node at
the plucked point should not be excited is completely set aside. A
possible mechanical explanation of this result is suggested.
From the RMIM Article Archive maintained by Satish Subramanian