6 of the best iOS MIDI controller apps | MusicRadar
iConnectivity iConnectMIDI4+ 64 port MIDI interface for PC, MAC, and iOS
iRig MIDI Core MIDI interface for iPhone / iPod touch / iPad and SampleTank for iOS - YouTube
Amazon.com: Lighting to MIDI Cable, 6.6FT USB Type B OTG Cable 2.0 iOS Devices Compatible with Select iPhone,Midi Controller, Electronic Music Instrument, Midi Keyboard, Recording Audio Interface, USB Microphone : Musical Instruments