Extra notes were "added" to the mathematical arrangements -- forget the
'hand-played' labels -- on rolls because of one important fact:
thematic material must be added (a) to eliminate boredom from cascades
of notes that strike similarly, pneumatics not having the flexibility
of human fingers, and (b) to simulate accents that are impossible for the
Pianola to execute.

If you try a crescendo on the keyboard, beginning with P.P. -- the
loudest you'll get, with properly-voiced hammers, is something in the
neighborhood of accented m.f. (but not quite F. -- or forte).  F.F. and
sFz (sforzando) are impossible!  (Don't remove your fingers from the
keys for this crescendo "test"!)

When I simulate Max Morath or William Albright or Frank French on a
roll -- when they "whap" a loud bass octave -- I add extra notes, but
only for a flash.  This creates the illusion of a specific pianist.

If one plays the exact notes the artist did, any roll is totally boring
and lifeless, lacking the human striking flexibility.

Remember -- your fingers can descend to the keys, but the player has
them resting there, just as I suggested in the "test" above.  If you
repeat that "test" with the fingers coming down a 1/4" or a 1/2" or
more, you'll get an exciting accent, and the crescendo continues with
F., F.F. and sFz.  In other words, you get the complete spectrum of the
pianoforte from the keyboard and only about 1/2 to 2/3 from the
pneumatics.

Half the music wasn't copyrighted in the old days, even though the
labels said so.  Much of the time royalties were never paid, as in the
case of LeClerc's QRS roll of Triangle Jazz Blues (1917).  (See my
web site for the story on this selection, involving pianist Wally Rose
in the early 'Fifties.)

Douglas Henderson