---
title: PHASEMetaParameterDefinition
framework: phase
role: symbol
role_heading: Class
path: phase/phasemetaparameterdefinition
---

# PHASEMetaParameterDefinition

A specification for a named parameter with a constant value.

## Declaration

```swift
class PHASEMetaParameterDefinition
```

## Overview

Overview Instances of this class provide an app with dynamic control of various properies of live audio playback. This is a base class for the PHASENumberMetaParameterDefinition and PHASEStringMetaParameterDefinition subclasses. You create a single instance of one of the subclasses for a specific property you want to adjust. By passing the definition subclass to the framework, you spawn one or more PHASEMetaParameterDefinition objects for discrete use across your app. For example, when you initialize a PHASEBlendNodeDefinition with a number metaparameter definition, PHASE registers a PHASENumberMetaParameter in the corresponding sound event’s metaParameters dictionary. Put metaparameter definitions that you wish to share across different sounds in the asset registery’s globalMetaParameters dictionary. To add global metaparameter definitions to the dictionary, call  registerGlobalMetaParameter(metaParameterDefinition:). Then pass the definition into several sound event node defintions, such as PHASESamplerNodeDefinition.

## Topics

### Setting a Metaparameter

- [value](phase/phasemetaparameterdefinition/value.md)

## Relationships

### Inherits From

- [PHASEDefinition](phase/phasedefinition.md)

### Inherited By

- [PHASENumberMetaParameterDefinition](phase/phasenumbermetaparameterdefinition.md)
- [PHASEStringMetaParameterDefinition](phase/phasestringmetaparameterdefinition.md)

### Conforms To

- [CVarArg](swift/cvararg.md)
- [CustomDebugStringConvertible](swift/customdebugstringconvertible.md)
- [CustomStringConvertible](swift/customstringconvertible.md)
- [Equatable](swift/equatable.md)
- [Hashable](swift/hashable.md)
- [NSObjectProtocol](objectivec/nsobjectprotocol.md)

## See Also

### Base Metaparameters

- [PHASEMetaParameter](phase/phasemetaparameter.md)
- [PHASEGlobalMetaParameterAsset](phase/phaseglobalmetaparameterasset.md)