<CoreFoundation/CoreFoundation.h>,
<CoreServices/CoreServices.h>,
<CoreMIDI/MIDIServices.h>
This header defines functions to create MIDI play-through connections
between the MIDI sources and destinations. These connections may be
persistent or transitory, owned by a client.
By using connections instead of doing MIDI Thru operations themselves,
the overhead of moving MIDI messages between the server and the client
for thru-ing is reduced.
The aim of these functions is to permit as flexible a set of transformations
as possible while keeping the API and data structures relatively simple.