# MIDIDestinationCreateWithProtocol(_:_:_:_:_:) Creates a virtual destination in a client. ``` func MIDIDestinationCreateWithProtocol(_ client: MIDIClientRef, _ name: CFString, _ protocol: MIDIProtocolID, _ outDest: UnsafeMutablePointer, _ readBlock: @escaping MIDIReceiveBlock) -> OSStatus ``` ## Parameters `client` The client that owns the virtual destination. `name` The name of the virtual destination. `protocol` The MIDI protocol variant to deliver to the destination. The system automatically converts messages to this protocol as needed. `outDest` On successful return, a pointer to the newly created destination. `readBlock` A callback block the system invokes when a client sends MIDI data to the virtual destination. ## Return Value An `OSStatus` result code. ## Discussion Drivers don’t need to call this function. When they create devices and entities, the system automatically creates sources and destinations at that time. See [`kMIDIPropertyAdvanceScheduleTimeMuSec`](/documentation/CoreMIDI/kMIDIPropertyAdvanceScheduleTimeMuSec) for information about the relationship between when a sender sends MIDI data to the destination and when it’s received. The system calls the read block on a separate high-priority thread owned by Core MIDI. > Tip: > After creating a virtual source, assign it the same unique ID it had the last time your app created it. Doing so permits other clients to retain persistent references to your virtual source. --- 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)