Regards an orchestrion containing piano and other instruments, I would
imagine that you tune the piano to any fixed pitched instrument which
forms a part of the orchestrion, e.g., xylophone, organ pipes, etc.

The important thing is, the orchestrion is in tune with itself.  The
actual pitch of any musical instrument is purely nominal.

If the orchestrion does not contain a piano, then tune the pipes to a
fixed pitch instrument.  If the orchestrion contains pipes only, the
pitch should be marked on some of the pipes.  If not, it should be
obvious, by reference to a sample of pipes, which pitch it was
originally built to, a job made easier if some of the pipes are cut
dead length.

If all pipes contain some sort of tuning device, then it should be
possible to alter the tuning slightly, from one pitch standard to the
next, providing the change is small.  Hope this helps.

Steve Toyne
Boston, England