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# MIDI Capability Inquiry

Provide support for bidirectional discovery and configuration of devices.

## Discussion

MIDI Capability Inquiry (MIDI-CI) uses bidirectional communication to enable devices to exchange information about their capabilities and automatically configure themselves to work together. MIDI-CI discovers and configures devices using the following means:

- Profile configuration. Profiles define a standard set of rules for how devices respond to MIDI messages. For example, devices that support a piano profile respond to messages common to a piano, such as note on and off, velocity, and pedaling.
- Property exchange. Devices can use a set of System Exclusive (SysEx) messages to find and control various properties of other devices.
- Protocol negotiation. MIDI 2.0 devices can select between using the MIDI 1.0 or 2.0 protocols, falling back to 1.0 when not supported by other devices.

MIDI-CI defines two roles in the communication between devices: *initiator* and *responder*. Client processes acting as the initiator use the [`MIDICISession`](/documentation/CoreMIDI/MIDICISession) API, which allows for profile and property configuration of the associated responder. Client processes that advertise their own profile and property capabilities use the [`MIDICIResponder`](/documentation/CoreMIDI/MIDICIResponder) API, which sends responder-originated messages to initiators.

## Topics

### Capability Inquiry

[`MIDICIDiscoveryManager`](/documentation/CoreMIDI/MIDICIDiscoveryManager)

A singleton object that performs systemwide MIDI-CI discovery.

[`MIDICISession`](/documentation/CoreMIDI/MIDICISession)

An object that represents a MIDI-CI session.

[`MIDICIProfile`](/documentation/CoreMIDI/MIDICIProfile)

A mapping of MIDI messages to specific sounds and synthesis behaviors, such as General MIDI, a drawbar organ, and so on.

[`MIDICIProfileState`](/documentation/CoreMIDI/MIDICIProfileState)

An object that provides the enabled and disabled profiles for a MIDI channel or port on a device.

[`MIDICIProfileStateList`](/documentation/CoreMIDI/MIDICIProfileStateList)

An array of profile state objects that describes the profile configuration for all channels of a reachable MIDI-CI node.

[`MIDICIResponder`](/documentation/CoreMIDI/MIDICIResponder)

An object that responds to MIDI-CI inquiries from an initiator on behalf of a MIDI client, and handles profile and property exchange operations.


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