---
title: "callAudioUnit(_:)"
framework: audiotoolbox
role: symbol
role_heading: Instance Method
path: "audiotoolbox/aumessagechannel/callaudiounit(_:)"
---

# callAudioUnit(_:)

Sends an audio unit a custom data message.

## Declaration

```swift
optional func callAudioUnit(_ message: [AnyHashable : Any]) -> [AnyHashable : Any]
```

## Parameters

- `message`: The data to send the audio unit.

## Return Value

Return Value A dictionary with custom data.

## Discussion

Discussion The valid values for key and value types are NSArray, NSDictionary, NSOrderedSet, NSSet, NSString, NSData, NSNull, NSNumber, and NSDate.