# HostCallback_GetBeatAndTempo When called by the system, provides beat and tempo information to an audio unit from a host application. ``` typealias HostCallback_GetBeatAndTempo = (UnsafeMutableRawPointer?, UnsafeMutablePointer?, UnsafeMutablePointer?) -> OSStatus ``` ## Parameters `inHostUserData` Custom data that you provided when registering your callback with the audio unit. `outCurrentBeat` On output, the current beat of the music that is playing. `outCurrentTempo` On output, the current tempo of the music that is playing. ## Discussion If you named your callback function `MyHostCallback_GetBeatAndTempo`, you would declare it like this: --- 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)