RussellMc wrote:
> I looked at the page cited and thought about that description.
> It's not obvious (to me) from what is said there  two LEDs aid this
> effect more than one would.

I must say I've never tried this nor seen such a device (with two strobed
light sources) in use.  However, it makes sense to me.  If you had a single
strobe, the string would be frozen in space at one part of its cycle when
exactly in tune.  When out of tune, it would appear to move thru its cycle
at the beat frequency (amount out of tune).

I can see how this kind of display could be confusing, especially since the
string vibrations will decay in amplitude and perhaps have some low
frequency components you are not trying to tune for.  In other words, what'=
s
lacking is a reference to what a fixed point in the cycle is, since the
cycle itself is always changing.

I assume the two strobes are fired 180 degrees apart.  Now you can look at
the relative motion of what appears to be two strings.  This allows you to
see beat effects while visually ignoring changes in the overall cycle.  The
former make the strings move with respect to each other.  The later cause
both strings to mostly move together.


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