<!--
{
  "availability" : [
    "iOS: 16.0.0 -",
    "iPadOS: 16.0.0 -",
    "macCatalyst: 16.0.0 -",
    "macOS: 13.0.0 -",
    "visionOS: 1.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "AudioToolbox",
  "identifier" : "/documentation/AudioToolbox/AUMessageChannel/callAudioUnit(_:)",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Method",
  "symbol" : {
    "kind" : "Instance Method",
    "modules" : [
      "Audio Toolbox"
    ],
    "preciseIdentifier" : "c:objc(pl)AUMessageChannel(im)callAudioUnit:"
  },
  "title" : "callAudioUnit(_:)"
}
-->

# callAudioUnit(_:)

Sends an audio unit a custom data message.

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

## Parameters

`message`

The data to send the audio unit.

## Return Value

A dictionary with custom data.

## Discussion

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

---

Copyright &copy; 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)