Clearly, any hand-played roll will be hard to transcribe.  From what
I've been told, a practical if rather technical approach to deal with
the tempo variations and phrasing is to create a "click track" where
each beat or bar is marked by hand.  The performance can then be
stretched (so to speak) until the clicks are an equal distance apart,
which at least places all the notes within the right beat or bar rather
than purely randomly.  A friend who tried this achieved the stretching
by playing the MIDI and click tracks simultaneously in one sequencer
and recording in another set to synchronise on the clicks, but there
must be more direct approaches.

Regarding "manipulation", obviously the degree varies hugely, from
none to lots.  An interesting thing was pointed out at the weekend by
a friend about the extended notes in the middle of the scale that are
found in many rolls: he said that Fats Waller's disc recordings can
be heard to have this as well.  He really played that way!  His
contract stipulated that he must have a Steinway, and these come
with Sostenuto...  A technique learned from making rolls?  Who knows.

At Saturday's Player Piano Group AGM and dinner we were entertained
by jazz genius and historian Keith Nichols, who illustrated how jazz
pianists used thumb-played middle notes (shades of Thalberg) to flesh
out what would otherwise be rather dry performances, hence the Waller
observation.  So, don't be too cavalier about assuming what's been
added!

When it comes to popular rolls, however, one thing in the favour of
transcription is that almost without exception they are metrically-cut.
This is perfectly obvious from looking at the rolls, if they're laid
out a little.  The rollscanners group's efforts, particularly Warren
Trachtman's software that reconstructs the original perforation master,
make this even easier to spot, because you can count the punch rows
(or MIDI clicks) with software.

To help check the accuracy of reconstructed masters I've recently
added a facility to my piano roll editor to put lines across the roll
at fixed intervals, and most fox-trot-type dance rolls indeed come out
at 24 punch rows per beat.  So, if you scan a roll and do the proper
job on it of reconstructing the master, you will find that if the
bridging is removed you can directly display a roll master in music
notation in a suitable program.

Incidentally, during the rollscanners work, Anthony Robinson calculated
that a roll cut at 24 rows per beat with 20 rows per inch (which most
companies did) will deliver exactly the roll tempo in beats per minute,
i.e., a roll of Tempo 80 will have 80 beats per minute.  Presumably
this is no accident -- these were on the whole a very carefully-made
product whose makers knew exactly what they were doing!

Julian Dyer