Charlie Moore and I have been researching the differing arrangements 
of the tunes found on Roller Organ cobs, and I'm constantly amazed 
at the variety found.  They differ both in layout and harmony, pinning
patterns, style, sometimes even changing key.  (It's challenging
research, and Charlie is doing a _lot_ of work!)

So I'm curious: Do other instruments, such as pianos, etc., exhibit
these types of variances?  Or were they once mastered and never
changed?

Todd Augsburger - Roller Organs
www.rollerorgans.com

P.S. See the "work in progress" at http://cobs.rollerorgans.com/,
specifically the "Early Arrangements" and "Alternate Pinning Patterns"
menus.