for analysis, we employ Hilbert transformation to calcu-
late the magnitude of coordinations found in the bodily
movements.
2 Motions Studied
2.1 kneading
The potter kneads the clay in early stage of ceramic mak-
ing to prepare it for shaping. Kneading removes the air
contained in the clay and makes the clay evenly dense.
If the potter fails to knead the clay properly, the ceramic
is broken when it is burned in the oven due to the ex-
panded air. The motion of kneading is similar to that of
working dough in baking.
Kneading requires three to seven years to master. The
difficult point in kneading is that the potter has to knead
the clay very quickly, often in a few minutes, because
the clay gets dry due to the heat from his hands and the
dried clay is difficult to shape. He had better thus touch
the clay as shorter time as possible while kneading. It
is fairly difficult to push and form the clay on the desk
very quickly without touching it too much. That is why
it takes so long time to master kneading.
2.2 shaking
Ganza, or shaker, is a simple instrument widely used for
playing samba to produce rhythmic sounds. The instru-
ment we used for our experiment is a cylindrical shaker,
23 cm long and 6.5 cm diameter, and contains a handful
of small plastic balls within. The instrument produces a
characteristic dry noise when shaken quickly and a dim,
low-pitched noise when shaken slowly.
The difficulty in playing the shaker on samba rhythms
lies in producing the correct accents. Let H be high-
pitched, dry, short noise and L low-pitched, dim noise.
The shaker typically produces four patterns of H-L-L-H
for a measure, resulting in a 16 beat rhythm, i.e., H-L-L-
H H-L-L-H H-L-L-H H-L-L-H. The first H of H-L-L-H is
hit when the shaker is moved out and the following L is
hit when it is moved in towards the player’s head. The
next L is hit when the shaker is moved out again and
the following H is hit when it is moved in. To produce
the accents marked with H tone, the player has to move
the shaker quickly, for the first H when he moves it out
and for the second H when he moves it in. The same
asymmetry applies to the two L tones, too. Most learners
are confused by this asymmetric pattern, that is, moving
the arm out-in-out-in to produce the H-L-L-H pattern.
Producing the correct accents gets more difficult as the
tempo becomes faster.
3 Methods and Materials
3.1 motion capture
For both experiments, we used same experimental set-
tings with a few exceptions. For measurement, we used
MotionStar electro-magnetic motion capture system by
Ascention Corp. Its temporal resolution is 86.1 Hz. To
avoid magnetic interference, performance was done on a
wooden stage. 18 wired sensors were used. Their loca-
tions were as follows (see Figure 1):
• Left/Right Head: each lateral of the head, above the
respective ear. (no. 1 and 2)
• Left/Right Shoulder: top of each acromion. (no. 3
and 7)
• Left/Right Elbow: lateral of each olecranon. (no.
4/8).
• Left/Right Radius (lateral anterior wrist): lateral of
each distal of radius. (no. 5 and 9)
• Left/Right Ulnar (lateral posterior wrist): lateral of
each distal of ulnar. (no 6 and 10)
• Left/Right Hip: lateral of each crista illacae. (no. 11
and 12)
• Left/Right Thigh: lateral of each grater trochter.
(no. 13 and 16)
• Left/Right Knee: lateral of each humer condyle. (no.
14 and 17)
• Left/Right Ankle: lateral of each mallelous. (no. 15
and 18)
Figure 1: The bodymodel. Left: marker settings. Right:
Segments and joints. J denotes a joint and e denotes an
endpoint.
For samba shaking, the radius and ulnar sensors of
the other side were moved to each side of the shaker to
measure the wrist angle.
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