ON THE MAGIC OF
OVERTONE SINGING
Piero Cosi, Graziano Tisato
*ISTC-SFD – (ex IFD) CNR
Istituto di Scienze e Tecnologie della Cognizione – Sezione di Fonetica e Dialettologia
(ex Istituto di Fonetica e Dialettologia) – Consiglio Nazionale delle Ricerche
e-mail:
cosi@csrf.pd.cnr.it
tisato@tin.it
www:
I really like to remember that Franco was the first person I met when I
approached the “Centro di Studio per le Ricerche di Fonetica” and I still
have a greatly pleasant and happy sensation of that our first warm and
unexpectedly informal talk. It is quite obvious and it seems rhetorical to say
that I will never forget a man like Franco, but it is true, and that is, a part
from his quite relevant scientific work, mostly for his great heart and sincere
friendship.
1. ABSTRACT
For “special people” scientific interests some
times co-occur with personal “hobbies”. I
remember Franco talking to me about the “magic atmosphere” raised by the voice of
Demetrio Stratos, David Hykes or Tuvan
Khomei
1
singers and I still have clear in my mind
Franco’s attitude towards these “strange harmonic sounds”. It was more than a hobby but it
was also more than a scientific interest. I have to admit that Franco inspired my “almost
hidden”, a part from few very close “despera
te” family members, training in Overtone
Singing
2
. This overview about this wonderful musical art, without the aim to be a complete
scientific work, would like to be a small descriptive contribute to honor and remember
Franco’s wonderful friendship.
2. THE THROAT-SINGING TRADITION
Khomei
” or “Throat-Singing” is the name used in Tuva and Mongolia to describe a
large family of singing styles and techniques, in which a single vocalist simultaneously
produces two (or more) distinct tones. The lower one is the usual fundamental tone of the
voice and sounds as a sustained drone or a Scottish bagpipe sound. The second corresponds
to one of the harmonic partials and is like a resonating whistle in a high, or very high,
register. For convenience we will call it “diphonic” sound and “diphonia” this kind of
phenomenon.
Throat-Singing has almost entirely been an unknown form of art until rumours about
Tuva and the peculiar Tuvan musical culture spread in the West, especially in North
1
We transcribe in the simplest way the Tuva
n term, for the lack of agreement between the
different authors:
Khomei, Khöömii, Ho-Mi, Hö-M
i, Chöömej, C
höömij, Xöömij.
2
This is the term used in the musical cont
est to indicate the diphonic vocal techniques.
Am
erica, thanks to Richa
rd Feynm
an [1]
3
, a distinguishe
d Am
erican phy
sicist, who wa
s an
arde
nt dev
otee of
Tu
van matters.
Th
is si
nging trad
itio
n is mo
stly p
racticed
in th
e Central Asia
reg
ions in
cluding
Bashkortostan
or Bashkiria (near Ural m
ount
ains),
Kazakhs
tan, Uz
bekista
n, Altai and T
uva
(two autonom
ous
re
publ
ics of t
he R
ussi
an Fede
rat
ion),
Kha
kassi
a a
nd M
ongolia (Fi
g. 1),
but
we ca
n fi
nd e
xam
ples
wo
rldwide: in Sout
h Af
rica bet
ween X
osa wom
en [3]
, in the
Tibet
an B
uddhist chant
s and i
n Rajast
an.
The T
uvan
p
eopl
e
devel
oped
num
ero
us diffe
rent st
yles. T
he m
ost import
ant are:
Ka
rgyraa
(ch
ant with v
ery lo
w fu
nd
am
entals),
Khom
ei
(it is th
e n
ame generally u
sed to
indicate the
Throat-Singing a
nd also
a pa
rticular t
ype of singing),
Bo
rbangn
adyr
(sim
ilar
to
Ka
rgyraa
, wi
th higher fundam
ent
als),
Eze
ngileer
(recogn
izab
le
by the qu
ick rh
yth
mical
shifts b
etween th
e d
iphon
ic h
arm
onics),
Sygyt
(lik
e a whistle, with
a weak
fund
am
ental)
[4]. Accord
ing to
Tu
van trad
itio
n, all th
ing
s have a so
ul or are i
nhabited by
spi
ritual
entities. Th
e leg
end
s narrate th
at Tu
van learn
t to
sing
Kh
omei
to establish a contact
and
assi
mila
te th
eir
pow
er trou
gh th
e i
mitat
ion of natur
al sound
s. Tuv
an peop
le b
eliev
e in fact
that th
e sou
nd is th
e way p
referred
by th
e sp
irits o
f nature to
reveal th
em
selv
es an
d to
comm
unicate with
th
e o
ther liv
ing b
eings.
Figure
1. Di
ffusion of the Throat-Si
ngi
ng in Central
Asia re
gions.
In M
ongo
lia mo
st Th
roat-
Singing
styles take
the nam
e from the part
of t
he body w
here
they su
ppose
to feel
the vi
bratory
resonance:
Xamry
n Xöömi
(nasal
Xöö
mi
),
Bagal
zuury
n
Xöömi
(th
roat
Xöömi
),
Tseedznii
öm
i
(ch
est
Xööm
i
),
Kevliin
Xöömi
(ventral
Xöö
mi
, see
Fig. 13
),
Xa
rkiraa
Xöö
mi
(si
milar to
th
e Tu
van
Karg
yraa
),
Isgerex
(ra
rely used style: it
sounds like a flute). It ha
ppe
ns th
at the singers itself confuse th
e di
ffe
rent sty
les [5]
. Som
e
very
fam
ous M
ongol art
ists (S
undui an
d Ga
nbol
d, for ex
am
ple)
use a
deep
vi
brato, which is
not tradition
al, may b
e to
im
itate th
e Western
singers (Fig.
13).
The Khakas
h people practic
e thre
e types
of Th
roat-Si
nging (
Ka
rgirar
,
Ku
ved
er
or
Kilen
ge
and
Sigirtip
), e
qui
val
ent to the Tu
van st
yles
Ka
rgyraa
,
Eze
ngile
er
and
Sygyt
. We
3
Today, partly because of Feynm
an’s influen
ce, the
re e
xists a s
ociety calle
d “Friends
of
Tu
va” i
n California, which ci
rcul
ates
new
s about Tuva i
n the West [2]
.
find
ag
ain th
e sam
e styles
in th
e p
eoples
of the Altai Mo
un
tain
s wit
h th
e n
ames o
f
Ka
rkira
,
Kio
mioi
and
Sibiski
. The
Bas
hki
ria m
usical
tradition
uses t
he T
hroat-Si
nging
(called
Uzla
u
,
similar to
th
e Tuv
an
Eze
ngil
eer
) to acc
om
pany the
epic
chants
. In Uz
bekistan, Kaza
khstan
and K
arakalpakstan w
e find
forms o
f or
al poetr
y w
ith
diphon
ic h
armonics
[6].
The Ti
bet
an
Gy
uto m
onks hav
e al
so a
tradi
tion
of di
phonic cha
nt, rel
ated t
o the
relig
iou
s believ
es of the vibrato
ry reality o
f th
e universe.
Th
ey chan
t in
a v
ery l
ow register
in a way that resem
bles (see later the difference) t
he T
uva
n
Ka
rgyraa
method. T
he ai
m of
this trad
ition
is mystical an
d consists in
iso
latin
g the 5
th
or th
e 10
th
ha
rm
oni
c partial of
the
vocal sou
nd. Th
ey pro
duce in
th
is
way th
e in
terv
als
of 3
rd
or 5
th
(in
relatio
n to th
e
fund
am
ental) th
at h
ave a symb
olic
relatio
n with
the
fire
and water elem
ents (Fig
. 14) [4]
.
Fig
ure 2. Sp
ectr
al sectio
n of
a vo
cal (up
) and a d
iphon
ic vo
cal (
dow
n).
3.
SEPA
RATI
ON O
F THE
AUDIT
ORY IMAGE I
N THRO
AT-
SIN
GIN
G
What
is so w
onde
rful in Th
roat-Si
ngi
ng? It is the appeara
nce of
one
of
the harm
oni
c
partials th
at d
isclo
ses th
e secret
musical n
ature
of each
sou
nd. When
in Th
roat-Sing
ing th
e
voice sp
lits in
two
d
ifferen
t so
un
ds, we
experien
ce th
e u
nusual sen
satio
n of a p
ure,
discar
nat
e, si
ne wa
ve em
ergi
ng from
the s
ound. It is the same ast
oni
shment w
e fe
el w
hen
we see
a rai
nbow, em
erging from
the white
light,
or a lase
r beam
for t
he first tim
e.
The
nat
ural
sounds
have a
complex st
ruct
ure
of harm
onic or
inharm
oni
c si
nusoidal
part
ials, cal
led “overt
ones
” (Fig. 2
). These
ove
rtones
are not
hea
rd as di
stinct sounds, but
their relativ
e in
ten
sity d
efin
es ou
r p
ercep
tio
n of all th
e param
eters of
sound
(in
tensity,
pitch, timbre,
durat
ion).
The pitch c
orresponds
to the com
mon fre
quency
di
stance
bet
ween
the partials and the timbre takes into account all the partials as a whole. The temporal
evolution of these components is what makes
the sound of each voice
or instrument unique
and identifiable.
In the harmonic sounds, as the voice, th
e components are at the same frequency
distance: their frequency is a multiple of the
fundamental tone (Fig.
2). If the fundamental
frequency is 100 Hz, the 2
nd
harmonic frequency is 200 Hz; the 3
rd
harmonic frequency is
300 Hz, and so on. The harmonic partials of a sound form a natural musical scale of
unequal temperament, as whose in use during the Renaissance [7]. If we only take into
consideration the harmonics that are easy to pro
duce (and to perceive also), i.e. from the 5
th
to the 13
th
, and if we assume for convenience a C3 131 Hz as starting pitch, we can get the
following musical notes:
Harm. N.
Freq. (Hz)
Note
Interval with C3
5 655 E5 3
rd
6 786 G5 5
th
7 917 A+ 6
th
+
8 1048 C6 Octave
9 1179 D6 2
nd
10 1310 E6 3
rd
11 1441 F6+ 4
th
+
12 1572 G6 5
th
13 1703 A6- 6
th
The series of 8
th
, 9
th
, 10
th
, 12
th
, 13
th
harmonic and the series from 6
th
to 10
th
are two
possible pentatonic scales to pl
ay. Note that the frequency differences between these scales
and the tempered scale are on the order of 1/8th of a tone (about 1.5%).
The Throat-Singing allows extracting the notes of a natural melody from the body of the
sound itself.
The spectral envelope of the overtones is essential for the language comprehension. The
glottal sound is filtered by the action of the vo
cal tract articulation, shaping the partials in
the voice with some characteristic zones
of resonance (called formants), where the
components are intensified, and zones of anti-resonance, where the partials are attenuated
(Fig. 2-3). So, the overtones allow us to tell apart the different vocal sounds. For example
the sounds /a/, /e/, /i/, /o/, etc. uttered or sung at the same pitch, nevertheless sound different
to our ears for the different energy distribution of the formants (Fig. 2).
The auditory mechanisms “fus
e” the partials in one single “image”, which we identify
as voice, musical instrument, noise, etc. [8]. In the same way, the processing of visual data
tends to group different dots into simple shapes
(circle, triangle, square, etc.). The creation
of auditory images is functional to single out and to give a meaning to the sonic sources
around us.
The hearing mechanisms organize the stream of perceptive data belonging to different
components of different sounds, according to
psychoacoustics and Gestalt principles. The
“grouping by harmonicity”, for example, allows the fusion in the same sound of the
frequency partials, which are multiples of a common fundamental. The “common fate”
principle tells that we integrate the components of a complex sound, which show the same
amplitude and frequency behaviour (i.e. similar modulation and microvariation, similar
attack and decay, similar vibrato, etc.) [8].
If one of these partials reveals a particular
evolution (i.e. it is mistuned or has not the same frequency and amplitude modulation, etc.),
it will b
e heard
as a
sep
arat
e sou
nd. So
th
e Th
roat-Si
nging
is a m
arvelou
s ex
am
ple to
understand
th
e illu
sory
nature
of percep
tion
and th
e m
usical stru
cture
of th
e sou
nd.
Figure
3. R
esona
nce
en
vel
ope
for a
n uniform
vocal
tract (l
eft
). A c
onst
riction on the
pharynx
m
oves th
e form
ants so
th
at th
e inten
sity o
f partials in
th
e 25
00
-35
00 Hz
region
increases
(right).
4.
FUN
DAME
NTAL TECH
NIQUES
IN
THRO
AT-
SIN
GIN
G
In t
he T
hroat-Singi
ng t
he si
nge
r l
ear
n t
o art
iculate the vocal tract so
that one
of the
form
ant
s (usua
lly the fi
rst
or
the seco
nd) c
oincide
with the desi
red
har
moni
c, gi
ving it a
con
sidera
ble ampli
tude i
ncre
ase (eve
n m
ore t
han
30
dB
, see i
n Fi
g.
2 t
he 1
0
th
ha
rm
oni
c)
and m
aking it perce
ptible. Unlike the normal
speech, t
he diphonic ha
rmonic ca
n excee
d a
lot th
e lo
wer
partials in
ten
sity (Fig
. 2
). Sop
rano
sin
gers
use similar sk
ill
to co
ntrol th
e
position
of th
e 1
st
fo
rm
ant
, tuni
ng i
t to the fu
ndam
ental with
th
e prop
er articu
latio
n (i.e.
proper
openi
ng of the m
out
h),
when they wa
nt to sing a high not
e [9].
There a
re m
any di
ffere
nt m
ethods t
o produce t
he di
phonic so
und [
5-6], but we ca
n
summ
arize the
m in two
pos
sible categories,
called “single
cavity
method” or “t
wo c
avit
ies
method”,
that are c
haract
eri
zed
by the use
or not of the tongue
, acc
ording to the proposal of
Tran Qu
ang Hai [
4].
4.1 SINGLE
CAVITY
METHOD
In th
is m
ethod, th
e to
ngu
e do
esn
’t m
ove an
d rem
ains flat o
r slig
htly cu
rved witho
ut
touching
th
e palate. In
th
is case th
e v
ocal
tract is
lik
e a co
ntinu
ous tu
be (Fig
. 3). Th
e
sel
ect
ion o
f the di
phonic har
moni
c is obt
ained
by the ap
propriate o
pening o
f the m
out
h and
the lip
s. Th
e resu
lt is th
at the form
ants freq
uency raises
if th
e vocal tract len
gthens (for
exam
ple with
a /i/) an
d that the form
ants frequ
ency l
owers, i
f it ex
tend
s (for ex
am
ple with a
/u/). With
this tech
niqu
e the 1
st
fo
rm
ant m
ovement allo
ws th
e selection
of th
e partials. As
we can see i
n Fig. 4
, we ca
nnot
go beyond 12
00
Hz. T
he di
phonic har
moni
c i
s gener
ally
feeble, m
asked by the fundam
ental and the l
owe
r p
artials, so
th
e sing
ers
nasalize th
e sou
nd
to redu
ce th
eir inten
sity [10-11
].
Figure 4
. Opening t
he m
out
h cont
rol
s the 1
st
form
ant p
ositio
n. The m
ovemen
t of th
e tong
ue
affects t
he 2
nd
fo
rm
ant and
allo
ws th
e h
arm
onic selectio
n in a larg
e freq
uency rang
e.
4.2 TWO
CAVIT
IES
METHODS
In th
is m
ethod, th
e to
ng
ue is raised
so
to
divide th
e vo
cal tract in
two
main
reson
ators,
each one tune
d on a pa
rticular resona
nce. B
y an
appropria
te control, we
can obtain to tune
two se
parat
e harm
oni
cs, an
d there
by to m
ake
perce
ptible, not
one b
ut two (or more) pi
tches
at the sam
e time (Fi
g. 9-12)
.
There a
re thr
ee po
ssible variants
of t
his technique:
Th
e first co
rresp
ond
s to
th
e
Kh
omei
style:
to select th
e d
esired
harm
onic th
e tip
of th
e
tongue
an
d t
he tongue
body m
ove
s forwa
rd (higher
pi
tch) and bac
kwar
d (lowe
r pitch) along
the p
alate.
The sec
ond is
cha
racteristic of the
Sygyt
style: th
e tip
of the t
ongu
e rem
ains fix
ed
behind th
e up
per
teeth
wh
ile th
e tong
ue body r
ises to select th
e harmonics.
In t
he t
hird variant
, the m
ovem
ent of t
he t
ongue r
oot sel
ect
s t
he di
phonic ha
rm
oni
c.
Sh
ifting
the base of th
e t
ongue near t
he posterio
r wall of th
e thro
at, we ob
tain
th
e lower
harm
oni
cs.
On the c
ont
rary, movi
ng t
he ba
se o
f the t
ongue fo
rward,
we
pul
l out
the highe
r
harm
oni
cs [6]
.
A di
ffe
rent method has bee
n pr
opose
d by Tra
n Qua
ng Hai
to pr
oduce
very hi
gh
diphonic ha
rm
oni
cs (
but not
to cont
rol
the sel
ect
ion of t
he desi
red c
omponent). It
co
nsists

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