Hello Timkeys,
unfortunately no. We would be infringing copyright. Read this: https://forums.irealpro.com/threads/48/
Melodies and lyrics are subject to copyright.
computer software like a DAW, Logic, Cubase, Garageband, Sibelius etc. can do this already.
Do you mean a iPhone app? iReal Book is purely a visual chart viewer, not playback/midi software so wouldn't you want a completely different app. altogether for midi?
Timkeys
There are some midi apps on the iTunes app. store. Some of these import and play midi files. Here is one I found which might be useful for you, called Midi Player: