Following the discussion of these standards, I knew I'd read something
that covered more than just the 9 holes per inch bit of the standard.
This is in 'AMICA Technicalities' number 1, page 42, reprinting a letter
from QRS saying their rolls meet the standards. Hope I'm not repeating
something everyone knows.

I assume these are the same as the standards we usually refer to from
1908. Does anybody know the text of the original agreement?

Anyway, these standards do not cover the tracker bar profile. I can't
see that a particular profile is important for playing a roll, and would
expect the geometry of the spool box to determine such things as the
curvature of the tracker bar face.

Interestingly, the most detailed specification is the minimum area for a
single perforation. Perhaps this is of use when constructing electronic
valve devices to ensure sufficient air is admitted?

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Music Roll Standards
Adopted at a trade convention, Chicago, Feb 13 1911.

Perforations shall be spaced at nine to the inch.

Paper shall be 11.25 inches wide.

Music notes to be centered on the paper.

The distance from the inside of the flange on the drive spool end to the
end of its base socket shall be 5/16".

The socket on the drive spool end shall be not less than 1/8", and the
depth of the slot not less than 1/4".

The tempo shall be such that when at 70, seven feet of paper pass over
the tracker bar per minute; eight feet at tempo 80, and so on.

Perforations along margins are recommended to be the same size as the
music perforations, and the sustaining perforations to be the third
perforation from the last playing note at the bass end of the sheet.

Length of the shortest bridge between playing notes (repeating) to be
not less than 0.110".

The diameter of the smallest perforation to be not less than 0.0595".

The length of the smallest perforation in the music roll shall be not
less than 0.083" when the width does not exceed 0.060", or if the width
of the perforation be greater than 0.060", then its length shall be not
less than is sufficient to give an area of the perforation equivalent to
that of a perforation 0.0595" in width by 0.083" in length.

The maximum vertical diameter of the orifices of the tracker bar for
speaking pneumatics shall not exceed 0.089".

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Julian Dyer