music and latency

[Robert Port <port@xxxxxxxxxxxxxx>]

The problem of adapting to delays in motor control is surely nothing
unique to musicians and generally requires little or no practice to
achieve.  Ordinary people can do this with ease. Try tapping a pen on
the desk with your left hand and simultaneously slap a very flexible
ruler on the desk with the other.  Of course, if you move your wrists
simultaneously, the ruler will slap later than the pen. It takes only
about 2 strokes for your right hand to phase shift so that the two
sounds are simultaneous.  It works just as well if someone else is
making the series of taps (instead of your left hand). Or better yet,
alternate the left and right hands.  Many tools create this latency
problem but as long as there is a salient auditory consequence of the
motion, people will adjust the gesture timing to put the auditory
effect where they want it.  Of course, when the phase shift is large -
eg, greater than a half a cycle -- it becomes much more difficult to
do.
        I did an unpublished experiment on this some years ago using a
metronome and a computer key that had controllable delays before
producing a beep. Nonmusician subjects found the task (to produce
beeps simultaneous with the metronome) very easy until the delay was
large relative to the metronome period.
        Bob Port

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                       Lingstcs/Comp Sci/Cogntv Sci
   ROBERT F. PORT      330 Memorial Hall, Indiana University
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