# MIDISourceCreateWithProtocol(_:_:_:_:) Creates a virtual source in a client. ``` func MIDISourceCreateWithProtocol(_ client: MIDIClientRef, _ name: CFString, _ protocol: MIDIProtocolID, _ outSrc: UnsafeMutablePointer) -> OSStatus ``` ## Parameters `client` The client to own the virtual source. `name` The name of the virtual source. `protocol` The MIDI protocol variant to send from this source. The system automatically converts messages from this protocol to the protocol of the destination. `outSrc` On successful return, a pointer to the newly created source. ## 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. After creating a virtual source, use [`MIDIReceivedEventList(_:_:)`](/documentation/CoreMIDI/MIDIReceivedEventList(_:_:)) to transmit MIDI messages from your virtual source to any clients connected to the virtual source. > 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)