Benjamin Intartaglia asked a number of questions concerning the piano
rolls by Thomas Waller which were released by QRS during the 1920s
and J. Lawrence Cook's involvement in their production. Some years ago
I thoroughly researched this very subject; a copy of my report is held
in the MMD archives so if Benjamin would care to read it he will find
some of the answers there.

 [ See the rollography at http://mmd.foxtail.com/MMMedia/index.html

What were the circumstances leading to Fats' piano roll career with QRS?

According to the book by his son Maurice ("Fats Waller", published 1977
by Schirmer Books, New York), James P. Johnson, who was an established
QRS roll artist, wanted to go on the road for a while and figured that
Fats could take his place.  Fats was duly engaged.  This version of
events is largely repeated in Laurie Wright's definitive Waller
biography, "Fats In Fact", published 1992 by Storyville Publications,
UK.

There is much evidence to support the notion that J. Lawrence Cook had
an editorial role in shaping the final production copies of Fats' QRS
rolls.  Maurice's book mentions that Cook not only corrected mistakes
but would often add melody lines, employing a "third hand", by changing
holes and covering others.  After the roll was considered perfect, a
series of additional holes were perforated in the master to simulate
the sustaining notes because the marking piano was incapable of doing it.

John Farrell
http://homepages.tesco.net/~stridepiano/midifiles.htm