As was reported, we tuned the piano of our instruments to A=440 and
the xylophone was similarly tuned.  A piano at A=440 and a xylophone
at A=435 or any other frequency would sound awful.  When you hear a
nickelodeon with a xylophone that sounds really out of tune, the piano
tuning probably has gone lower while the xylophone has stayed the same.

Adjusting the tuning of a xylophone is not recommended.  It is too
easy to make things worse.  When we built the KT Specials we set up
a xylophone test bench able to play only the xylophone with a keyboard,
so not only could we get the tuning right but also the repetition rate
and the sound volume could be regulated perfectly, and also chords
could be played easily.

Regards,
Bill Edgerton