HWN: "(that took me some time figure out :-)
\autochange looks at the pitch of notes produced in the thread
belonging to the first element of a chord, in this case thread "tb".
This thread is completely empty during the first 10 measures, so
\autochange thinks nothing is happening. Switching the order of tb
and tc should solve the problem."
Han-Wen - you're a genius! I've been kicking the half dozen sonatas
around that had problems for days now, trying to see a pattern.
That's it.
(The reason those 1st measures were blank was because they had
contained notes that crossed the c' divide, so I had manually moved
them to another voice.)
I suggest adding the sentence
"\autochange looks at the pitch of notes produced in the first thread
of a voice, so this must contain a note if it belongs in the bass
clef."
to the refman note I sent you earlier.
Back to work - thanks.
John