The player piano tracker bar should be cleaned regularly with the use
of a tracker bar pump or other means which can vacuum dust from the
holes.  Some holes may accumulate dust faster than others.

How does this affect roll tracking?  It seems to me that if some holes
are clogged and others are less clogged, the player mechanism will tend
to play the notes which give the least resistance first.  Unlike the
non-perforated, non-note part of the paper, a note for a partially
clogged hole will try to play.  This situation certainly creates uneven
pressure across the tracker bar and in turn, affects the roll.

My question is:  Can partially clogged holes force a roll to go
off-track?

Just musing,

Joyce Brite
Player Piano and Mechanical Music Exchange
http://mmd.foxtail.com/Exchange/