Here's an overview about the methods of making piano rolls:

A.  Making rolls by hand

The simple, straightforward method is to place a roll of blank paper on
the kitchen table and cut slots with a sharp knife.  Timing marks may
be drawn beforehand, indicating the beats and the measure boundaries.
A template of the note positions may be drawn on the back of a wooden
ruler to guide the placement of the slots along the "note-axis".

I used a variant of the technique above for many years: after drawing
the timing marks and notes I would mount the roll in my vertical pumper
player, and cut the slots right at the tracker bar.  This ensures
proper hole placement.  (I didn't move the knife on the brass, though;
I moved the paper while the knife was stationary.)

Many rolls are still cut using a single-hole "frame punch", which has a
mechanical index provided for both the note-axis and the "time-axis"
positions.  The punch frame moves 6 to 12 inches along precise ways;
after that distance of punching is completed the paper must be
re-positioned and secured with clamps.

These hand methods were used for creating the majority of piano roll
titles through the mid 1920s.

B.  Pianos for "live recording"

Some companies built "recording pianos" to record classical music, in
which an external machine recorded the up-down positions of each key by
marking paper in some manner.  In most systems the piano key operated
an electric switch which activated an electromagnet to make an inked
line on the recording paper.  Then a technician would cut holes in the
paper where it was marked, or else use a pantograph to manually follow
the marks and punch holes in a fresh sheet of paper.

Mr. J. Lawrence Cook, the prolific arranger at QRS, had a "step-time"
perforator controlled by a keyboard.  Cook would hold down the chord
(sometimes aided by pencils stuck in keys which he couldn't reach) and
then kick a foot-lever which caused the perforator crankshaft to rotate
for one step.  He made thousands of rolls this way!

But because the recording pianos required significant maintenance, and
because popular rolls could often be created faster with a knife or
hand punch, the "drafting board" method is still used, especially for
editing the performance.

C.  Making rolls for pneumatic reproducing pianos

After a perforated "draft roll" was edited a technician would add all
of the extra holes to control the expression mechanism of the
reproducing piano.  The expression editor (usually a girl) was a
skilled musician who was familiar with the style of the performer, and
she worked and worked until the finished music roll sounded just like
the artist (sometimes even better!).  Expression editing of classical
rolls produced after the mid-1920s by Ampico and Welte (DeLuxe) was
aided by a recording of hammer velocity or key velocity.

Note that the reproduced music did not duplicate what the artist
recorded: the goal was to make a music roll which satisfied the artist
and the customer.  Ampico staged "comparison concerts" in which the
artist would alternate his live playing with an Ampico roll.  The
critics admitted they could not tell if the music was from the roll or
the live pianist.

The secret was simple: the pianist memorized and reproduced the sound
of the music roll, a task much easier than making a music roll memorize
the pianist's performance!

D.  Making disks for solenoid reproducing pianos

The Boesendorfer SE piano and the Yamaha Disklavier are controlled by
binary commands stored on a computer disk, just as the binary (on/off)
commands were traditionally stored as holes in a sheet of paper.  In
these contemporary pianos the velocity of each individual hammer is
recorded and reproduced.  Since few recording artists consider
themselves perfect performers there is always much manual editing to do
after the recording session, just as in the 1920s.  The biggest
difference is that nowadays the editing is done at the computer screen,
which displays an image much like a piano roll!  The disk file of the
performance can be used to control a perforator to make a piano roll
without expression.  (Coding for reproducing pianos may be added
manually.)

E.  Conclusion

The best performances are created by extremely skilled arrangers or
pianists, and brought to near-perfection by the efforts of the
equally-skilled editors.  The best classical music was recorded by
concert-quality pianists, and the best popular music rolls were
arranged by top-quality arrangers.  The pianist or arranger who was
less than top-notch wasn't invited back to record again!

[This manuscript has double spaces following the periods because it is
edited with a primitive mono-spaced font, like a typewriter.  I like it
that way!]

-- Robbie Rhodes