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  "documentType" : "symbol",
  "framework" : "PHASE",
  "identifier" : "/documentation/PHASE/PHASEMappedMetaParameterDefinition/envelope",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Property",
  "symbol" : {
    "kind" : "Instance Property",
    "modules" : [
      "PHASE"
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    "preciseIdentifier" : "c:objc(cs)PHASEMappedMetaParameterDefinition(py)envelope"
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  "title" : "envelope"
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# envelope

A collection of line segments that curve and connect to form a graph.

```
var envelope: PHASEEnvelope { get }
```

## Discussion

The line segments collectively plot an output value for the [`inputMetaParameterDefinition`](/documentation/PHASE/PHASEMappedMetaParameterDefinition/inputMetaParameterDefinition) property.

To plot the input, call [`evaluate(x:)`](/documentation/PHASE/PHASEEnvelope/evaluate(x:)), passing in the input metaparameter’s [`value`](/documentation/PHASE/PHASEMetaParameter/value).

To gradually change the input over time, call [`fade(value:duration:)`](/documentation/PHASE/PHASENumberMetaParameter/fade(value:duration:)).

---

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