---
title: parameterTree
framework: audiotoolbox
role: symbol
role_heading: Instance Property
path: audiotoolbox/auaudiounit/parametertree
---

# parameterTree

An audio unit’s parameters, organized in a tree hierarchy.

## Declaration

```swift
var parameterTree: AUParameterTree? { get set }
```

## Mentioned in

Migrating Your Audio Unit Host to the AUv3 API

## Discussion

Discussion Hosts can fetch this property to discover a unit’s parameters. KVO notifications are issued on this member to notify the host of changes to the set of available parameters. Subclasses should implement this property to expose parameters to hosts. They should then cache as much data as possible and send KVO notifications on this property when altering the structure of the tree or the static information of parameters. This version 3 property is similar to the version 2 kAudioUnitProperty_ParameterList and kAudioUnitProperty_ParameterInfo APIs.

## See Also

### Querying Parameters

- [allParameterValues](audiotoolbox/auaudiounit/allparametervalues.md)
- [parametersForOverview(withCount:)](audiotoolbox/auaudiounit/parametersforoverview(withcount:).md)