---
title: HostCallback_GetBeatAndTempo
framework: audiotoolbox
role: symbol
role_heading: Type Alias
path: audiotoolbox/hostcallback_getbeatandtempo
---

# HostCallback_GetBeatAndTempo

When called by the system, provides beat and tempo information to an audio unit from a host application.

## Declaration

```swift
typealias HostCallback_GetBeatAndTempo = (UnsafeMutableRawPointer?, UnsafeMutablePointer<Float64>?, UnsafeMutablePointer<Float64>?) -> 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

Discussion If you named your callback function MyHostCallback_GetBeatAndTempo, you would declare it like this:

## See Also

### Getting Information from the Host

- [HostCallback_GetMusicalTimeLocation](audiotoolbox/hostcallback_getmusicaltimelocation.md)
- [HostCallback_GetTransportState](audiotoolbox/hostcallback_gettransportstate.md)
- [HostCallback_GetTransportState2](audiotoolbox/hostcallback_gettransportstate2.md)
- [AUInputSamplesInOutputCallback](audiotoolbox/auinputsamplesinoutputcallback.md)
- [AUMIDIOutputCallback](audiotoolbox/aumidioutputcallback.md)