This is a cute applet. Now for the next step: MagicBaton for Linux! This is
somebody's trademark so call it Raton-Conductor.
MagicBaton was a MIDI conduction program for Windows 9*, marketed as a game,
from Japan. One used the mouse to actually conduct MIDI playback. Not as easy
as it sounds, even with the in-the-air gyro-mouse I bought for this purpose.
I saw potential in this, however, and suggested a more serious program.
Apparently, there is one in Japan. One correspondant on their site actually
used the program for choir rehearsals.
So how would Raton-Conductor work? Again, not as simple as it sounds.
Minimally, one would move the mouse in a ecliptic (or circular) motion (as
suggested by MagicBaton's instructions for beginners). The size of the
vertical diameter (or average diameter) would be the volume/expression and
tempo or time-codes set by the change in vertical direction from down to up.
Real conducting patterns are more complex but these two principals would more
or less remain.