In iOS 11, Apple added the ability to directly connect your iPad/iPhone to a Mac without any third-party software.

Open the Audio/MIDI App

Open Audio Devices... not MIDI Devices. Audio Devices!

You will see your connectable iPad/iPhone on the left side

Click "Enable"... you will hear a beep on your iOS devices and... you're done!

Check your MIDI Devices window to see the device enabled

Or check it in your favorite DAW

You'll note that in MIDI Designer the "No Connections" shingle drops off and that MIDI is flowing both ways... and fast.

Note: With our partners we made a product called musicIO, which Apple happily Sherlocked in iOS 11.