Electronic Sustain Timer

[Sarah Fox]

Hi Robert,

>  >This isn't nearly as complicated as it sounds.
>
> No, it's much more complicated.  I know because I have done it in TuneLab.
>
> If you look closely at the amplitude variations that occur as a note
> decays, you will see that even if only one string is sounding, there is
> still a beat-like variation due to the precession of the string from up
and
> down motion to its ultimate elliptical orbit.  Any falseness in the string
> makes matters even worse.

Actually my method takes that into account.  As the thresholds are crossed
(*both* the upper and lower thresholds), the beating will cause the timer to
switch in and out ("stuttering," if you will).  The final time reading will
be a reflection of the total time spent between the threshold bounds.  If
the beating is the same at the low amplitude (and then amplified 40 dB) as
it is at higher amplitude, the jittering across the thresholds should have
the same profile, and hence the demarcation of the "start" and "stop" times
will be equally "soft."  I don't know if I'm describing this clearly.  Does
it make sense???

The circuit I propose is *really* easy and lends itself well to repeat
measurements on many notes without time intensive calculations.  The method
you propose probably also works well.  However, an electronic method of
rectifying and averaging *somewhat* avoids the problem of the entry and exit
of harmonic components as their vibrational components "rotate" randomly
with respect to the fundamental.  Put another way, the peak profiles can
have weird beating patterns of their own, even when the RMS value of the
waveforms are the same.  I suspect this is a small point, though, and your
method should work fine.  Whatever works...

I'll check out Tune Lab.  Thanks!

Peace,
Sarah