I think the problem is more to do with your sound drivers then speakup.
This is pointed to by the modem also causing interferance. Making your
serial buffers larger may help, but it would also delay the amount of time
until you could silence the synth.
I would start by switching to ALSA drivers if you aren't already.
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Kirk Wood
Cpt.Kirk at 1tree.net
Nowlan's Theory:
He who hesitates is not only lost, but several miles from
the next freeway exit.
