One wonders if too much is being made of trying to find a linkage between
the term 'tracker' as used in the pipe organ business (mechanical linkage
between the keyboard and the pipe valves), and the way we use the word as
in 'tracker bar'.  It seems to me to be just another example of two words
of different origin ending up sounding the same.  This is a very common
occurrence in our multi-rooted language.

As for the origin of 'tracker' in organs; the problem seems to be that
the word itself is meaningless in that technical sense.  There is no
relationship between a wooden stick that pulls something and any natural
meaning of the verb 'track'.  One is left with the conclusion that the
word was a transliteration of some foreign term.  Although Mr. Kijlstra
must be correct that 'tracker' translates into 'Abstrakt' and related
terms, this is a technical equivalence, and does not necessarily
illuminate the origin of 'tracker' in English.

'Abstrakt' to 'tracker' seems to be an awkward shift, not typical of the
usual way such shifts happen (Grimm's Law).  It might be just as likely to
be a shift from the German 'Drucker' (pusher or actuator), considering
that Germans brought a lot of pipe organ technology to both the UK and
the USA.  Erie, PA, a hotbed of early American organ building, had so many
German immigrants that it was officially bilingual, including the public
schools, up until the First World War.

As for 'tracker' in the MM sense, it is much easier to imagine how the
word came to be so used; the tracker bar tracks, or follows, the music
roll.  Whoever originated the usage probably did not have any analogy to
the 'tracker organ' in mind.  What has always intrigued me about this
usage is this question: is 'tracker bar' a term-of-art from the era of
the device's origin, or is it a modernism like 'nickleodeon'?  The usage
has a sort of modern ring to it.  I know that early Aeolian literature
calls the thing a 'note-bar'.  People out there who are into original
manuals could help by indicating the earliest citation of 'tracker bar'
in literature contemporary to the player building era.

Richard Vance

 [ Those are good insights, Richard.  I hope that old industry
 [ literature will bring more information, as you suggest.  -- Robbie