# HostCallback_GetMusicalTimeLocation When called by the system, provides musical timing information to an audio unit from a host application. ``` typealias HostCallback_GetMusicalTimeLocation = (UnsafeMutableRawPointer?, UnsafeMutablePointer?, UnsafeMutablePointer?, UnsafeMutablePointer?, UnsafeMutablePointer?) -> OSStatus ``` ## Parameters `inHostUserData` Custom data that you provided when registering your callback with the audio unit. `outDeltaSampleOffsetToNextBeat` On output, the number of samples until the next beat. `outTimeSig_Numerator` On output, the numerator for a musical time signature. `outTimeSig_Denominator` On output, the denominator for a musical time signature. `outCurrentMeasureDownBeat` ## Discussion If you named your callback function `MyHostCallback_GetMusicalTimeLocation`, 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)