I am sorry I caused Mr. de Boer insomnia by raising the question as
to how a 65/88-note convertible player was made to work, but I am still
fascinated by the matter myself.

Another member wrote me privately that he had seen a convertible with
two rows of holes in the tracker bar, like the one described by Gray
Reassumes in his submission today.  I gather that the switch-over was
done by sliding the tracker bar itself, (or the piece behind it) so
that alternate ports on its rear face matched two different patterns
of holes on the rear block.  Rather like one switches up a semitone on
a chromatic mouth-organ.

I have also seen the Melville Clark Piano advertisement mentioned
by Mr. de Boer, which has been reproduced in the literature.  I think
the 'telescoping' device mentioned must refer to the mechanism for
converting the drive chuck from pin-end to modern 88-note flange
operation.

My push-up Pianola has a similar device for converting the drive end
from 65-note pin-end rolls to the less common flat-disk-end 65-note
'Universal' rolls.  A cylindrical piece slides out from the drive end
shaft and locks into place with a 'bayonet joint' to accommodate the
shorter overall length of the disk-end rolls.  'Telescoping' would be
a good description of this device.

A similar arrangement could be made to convert the drive shaft from
65-note pin-end to 88-note slot-end, if the chuck face had a slotted
hole for the pin, in the middle of the D-shaped 88-note drive tongue.

If another notch were cut in the bayonet lock, the length of the
roll-space could be adjusted to also accommodate the narrower 58-note
organ rolls.  These are also pin-end, punched 6/inch, and were very
common at that time.

A telescope device would not be required at the left end.  Only a small
hole in the center of the 88-note idler cone would be needed to accept
the tapered pin at the left end of 58 and 65-note rolls.  A long,
spring-loaded throw for the left chuck would be needed, to allow for
all the different roll lengths.

Now what is left unexplained in the Melville Clark ad are 70- and
82-note rolls.  I have never heard of such formats.  Perhaps that was
just advertising hype, perhaps based on formats that were being
discussed at the time, but never came to market.

Can anyone out there keep this thread alive by describing how a 65/88
convertible piano really works, and whether they always used two rows
of tracker ports, or one row of internally switched ports as I had
speculated?

Richard Vance