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Experiments showed that the proposed scheme works with reasonable
performance, though further studies are needed to investigate, for example,
the influence of the test sound and moving speed of sound objects.
8.5 Application to Computer Music Creation
Computer music is a particularly good example of applications at which the
sound feedback plays an important role. In this section we will demonstrate
how the proposed system is applied to collaborative computer music creation.
Here, there have been futuristic table-based computer music creation tools
that adopt tangible and gestural interfaces. Sound Rose [24] and the sys-
tem talked about by Davidson and Han [25] are musical table systems with
touch sensitive interfaces. The user creates music by touching the table with
finger(s). Block Jam [26], Audiopad [27], reacTable [28], and AudioCubes [29]
are tangible tabletop instruments for computer music, where manipulation
of plastic blocks on a table corresponds to music creation.
The system we propose in this paper uses a table as a means for interac-
tion as is similar to the above systems. However, a music sequence is speci-
fied by 3-D motion of a stick-type device over the table, rather than a touch
or an arrangement of music blocks on the table. Furthermore, our system is
capable of outputting sounds at different positions on the table. This helps
each of the players to sense others' performance, which is essential for col-
laborative music creation.
We have implemented several interface expressions to explore fundamen-
tal capabilities of the system. Here, as explained above, operation commands
for music creation are implemented by defining semantic descriptions for
the abovementioned gestures. For example, we assigned the following five
commands as to the trial demonstrated in Figure 8.10.
Drop (implemented by tilt) is an operation to newly create a sound object.
If the user tilts the stick device with keeping a button pressed, a sound object
is generated and spilled over the table. Each of the sound objects is visual-
ized with a certain color and shape as is seen in the figure. Their size and
loudness depend on the position of the stick device. The higher the spatial
position, the larger the circle size and the louder the generated sound.
Play and stop (implemented by attack) is an operation to switch between
play and stop of a sound. When the device is swung down over an object that
is sounding, the sound is terminated. At the same time, its color becomes
black so you can see the change. If the gesture is applied again, the object
restarts the sound.
Change (implemented by tap) is an operation to change sound sources.
A different color is assigned to each of the sound sources. At each time when
a tap gesture is placed on a sound object, its color and sound source change.
