Use MPE controllers with GarageBand for iPhone
You can use GarageBand with controllers that support MIDI Polyphonic Expression (MPE). MPE assigns each note to its own MIDI channel so that information about pitch, timbre, and expression controls are applied to notes individually.
Turn on support for MPE controllers
Open the Settings app, scroll down, then tap GarageBand.
Tap the Support MPE Controllers switch.
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