# BeginMix(ulong)

> Begin a mix.

## Definition

* **Type:** Method
* **Namespace:** [UnityEngine.Audio](/engine/6000.5/script-reference/unityengine/audio.md)
* **Assembly:** UnityEngine.AudioModule

```csharp
public RealtimeContext? BeginMix(ulong dspTick)
```

### Parameters

**** (\[ulong]\(https\://learn.microsoft.com/dotnet/api/system.uint64)): 

### Returns

| Type                                                                       | Description                                                                                                                                                                                                                                                                                                                                                                             |
| -------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [RealtimeContext?](https://learn.microsoft.com/dotnet/api/system.nullable) | A nullable [RealtimeContext](/engine/6000.5/script-reference/unityengine/audio/realtimecontext.md). This might hold no value in cases where audio is temporarily bypassed on the device, or similar. You should only [ControlContext.Manual.EndMix](/engine/6000.5/script-reference/unityengine/audio/controlcontext/manual/endmix.md) if there's a non-null return from this function. |

### Remarks

"Mixes" in Unity span a period of time where you can issue processing calls. They must be ended in pairs with a call to [ControlContext.Manual.EndMix](/engine/6000.5/script-reference/unityengine/audio/controlcontext/manual/endmix.md).