---
title: MIDIEventProc
framework: audiotoolbox
role: symbol
role_heading: Instance Property
path: audiotoolbox/audiooutputunitmidicallbacks/midieventproc
---

# MIDIEventProc

## Declaration

```swift
var MIDIEventProc: (UnsafeMutableRawPointer?, UInt32, UInt32, UInt32, UInt32) -> Void
```