I have used my iPad as a MIDI controller.  There are two ways to
connect it to the MIDI input on the player piano device, depending on
if it has a standard MIDI jack and/or USB port:

1. The Camera Connection Kit comes with a USB connector.  Use a USB
cable to connect the two devices.

2. iKey makes a MIDI called iRig.  It comes with a cable that connects
to the external device via a standard MIDI port.  An added benefit is
that the iRig also powers the iPad at the same time.  I bought one a
Guitar Center for around $65.

Then there is the controller software.  There are a number of apps
available that can output MIDI signals.  iRig comes with "SampleTank"
(free download from App Store).  I have not used it.  It appears that
you can load a MIDI file into it and play it.  I like "Music Studio 2."
You can import and export MIDI files.

As far as managing your MIDI files, the iPad will be of little help
because files are stored in the app.  If you want a MIDI file to be
used by two programs, each program will have a copy of the file on the
iPad.  There is no common file storage scheme.  Transfer to the iPad is
accomplished via iTunes unless the app has a wireless transfer method
built-in.

Mark Williams
boxermark@gmail.com.geentroep [delete ".geentroep" to reply]