AudioNode.connect

Syntax

var destinationNode = AudioNode.connect(destination, outputIndex, inputIndex);

AudioNode.connect(destination, outputIndex);

Parameters

destination

The AudioNode or AudioParam to which to connect.

outputIndex Optional

An index specifying which output of the current AudioNode to connect to the destination. The index numbers are defined according to the number of output channels (see Audio channels). While you can only connect a given output to a given input once (repeated attempts are ignored), you can connect an output to multiple inputs by calling connect() repeatedly. This makes fan-out possible. The default value is 0.

inputIndex Optional

An index describing which input of the destination you want to connect the current AudioNode to; the default is 0. The index numbers are defined according to the number of input channels (see Audio channels). It is possible to connect an AudioNode to another AudioNode, which in turn connects back to the first AudioNode, creating a cycle. This is allowed only if there is at least one DelayNode in the cycle. Otherwise, a NotSupportedError exception is thrown. This parameter is not allowed if the destination is an AudioParam.

Return value

If the destination is a node, connect() returns a reference to the destination AudioNode object. In some browsers, older implementations of this interface return undefined.

If the destination is an AudioParam, connect() returns undefined.

Exceptions

IndexSizeError

The value specified as outputIndex or inputIndex doesn't correspond to an existing input or output.

InvalidAccessError

The destination node is not part of the same audio context as the source node.

NotSupportedError

The specified connection would create a cycle (in which the audio loops back through the same nodes repeatedly) and there are no DelayNodes in the cycle to prevent the resulting waveform from getting stuck constructing the same audio frame indefinitely.

Connecting to an audio input

The most obvious use of the connect() method is to direct the audio output from one node into the audio input of another node for further processing. For example, you might send the audio from a MediaElementAudioSourceNode—that is, the audio from an HTML5 media element such as <audio>—through a band pass filter implemented using a BiquadFilterNode to reduce noise before then sending the audio along to the speakers.

Example

This example creates an oscillator, then links it to a gain node, so that the gain node controls the volume of the oscillator node.

var AudioContext = window.AudioContext || window.webkitAudioContext;

var audioCtx = new AudioContext();

var oscillator = audioCtx.createOscillator();
var gainNode = audioCtx.createGain();

oscillator.connect(gainNode);
gainNode.connect(audioCtx.destination);

Connecting to a parameter input

You can also connect the output of a node to a single input of an AudioParam (this is known as fan-in). This lets you easily use an audio signal to change the value of one or more parameters. A node's output can be connected to multiple AudioParams (allowing the node's output to control the value of multiple parameters—a technique known as fan-out), and multiple nodes can output their signal to a single AudioParam, too. Both of those scenarios are achieved through multiple calls to connect(), one for each node output to parameter pair.

Specifications

Specification	Status	Comment
Web Audio API The definition of 'connect() to an AudioNode' in that specification.	Working Draft
Web Audio API The definition of 'connect() to an AudioParam' in that specification.	Working Draft

Browser compatibility

See also

• Using the Web Audio API