# Core MIDI Data Types ## Topics ### Data Types [`typealias MIDICIDeviceID`](/documentation/CoreMIDI/MIDICIDeviceID) [`struct DictionaryKey`](/documentation/CoreMIDI/MIDICIDeviceManager/DictionaryKey) [`typealias MIDICIMUID`](/documentation/CoreMIDI/MIDICIMUID) [`struct MIDICIPropertyExchangeRequestID`](/documentation/CoreMIDI/MIDICIPropertyExchangeRequestID) [`typealias MIDIEventVisitor`](/documentation/CoreMIDI/MIDIEventVisitor) [`typealias MIDIUInteger14`](/documentation/CoreMIDI/MIDIUInteger14) [`typealias MIDIUInteger2`](/documentation/CoreMIDI/MIDIUInteger2) [`typealias MIDIUInteger28`](/documentation/CoreMIDI/MIDIUInteger28) [`typealias MIDIUInteger4`](/documentation/CoreMIDI/MIDIUInteger4) [`typealias MIDIUInteger7`](/documentation/CoreMIDI/MIDIUInteger7) [`struct DictionaryKey`](/documentation/CoreMIDI/MIDIUMPEndpointManager/DictionaryKey) [`typealias MIDIUMPFunctionBlockID`](/documentation/CoreMIDI/MIDIUMPFunctionBlockID) [`typealias MIDIUMPGroupNumber`](/documentation/CoreMIDI/MIDIUMPGroupNumber) [`typealias MIDICIDiscoveryResponseBlock`](/documentation/CoreMIDI/MIDICIDiscoveryResponseBlock) A block the system calls when a MIDI-CI node discovery request completes. [`typealias MIDICISessionDisconnectBlock`](/documentation/CoreMIDI/MIDICISessionDisconnectBlock) A block the system calls when a MIDI-CI session disconnects. [`typealias MIDIChannelNumber`](/documentation/CoreMIDI/MIDIChannelNumber) [`typealias MIDISetupRef`](/documentation/CoreMIDI/MIDISetupRef) A type that represents the global state of the MIDI system, that contains lists of the devices and serial port owners. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)