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# musicalContextBlock

A callback to the host for musical context information.

```
var musicalContextBlock: AUHostMusicalContextBlock? { get set }
```

## Discussion

An audio unit accessing this property should cache it in realtime-safe storage before beginning to render.

This version 3 property is bridged to the version 2 [`HostCallback_GetBeatAndTempo`](/documentation/AudioToolbox/HostCallback_GetBeatAndTempo) and [`HostCallback_GetMusicalTimeLocation`](/documentation/AudioToolbox/HostCallback_GetMusicalTimeLocation) callback members in the `kAudioUnitProperty_HostCallbacks` API.

---

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