FMOscillator implements a frequency modulation synthesis

+-------------+ +---------------+ +-------------+ | Carrier Osc | | Modulator Osc +>-------> GainNode | | +--->Output +---------------+ | +>----> frequency | +--> gain | +-------------+ | +-------------+ +-----------------+ | | modulationIndex +>--+ +-----------------+

return Tone.Offline(() => {
	const fmOsc = new Tone.FMOscillator({
		frequency: 200,
		type: "square",
		modulationType: "triangle",
		harmonicity: 0.2,
		modulationIndex: 3
}, 0.1, 1);



new FMOscillator (
frequency?:Frequency ,

The starting frequency of the oscillator.

type?:ToneOscillatorType ,

The type of the carrier oscillator.


The type of the modulator oscillator.

) => FMOscillator
new FMOscillator (
options?:Partial<FMConstructorOptions >
) => FMOscillator


baseType #


The oscillator type without the partialsCount appended to the end

const osc = new Tone.Oscillator();
osc.type = "sine2";
console.log(osc.baseType); // "sine"

blockTime #

readonly Seconds

The number of seconds of 1 processing block (128 samples)


channelCount #


channelCount is the number of channels used when up-mixing and down-mixing connections to any inputs to the node. The default value is 2 except for specific nodes where its value is specially determined.

channelCountMode #


channelCountMode determines how channels will be counted when up-mixing and down-mixing connections to any inputs to the node. The default value is "max". This attribute has no effect for nodes with no inputs.

  • "max" - computedNumberOfChannels is the maximum of the number of channels of all connections to an input. In this mode channelCount is ignored.
  • "clamped-max" - computedNumberOfChannels is determined as for "max" and then clamped to a maximum value of the given channelCount.
  • "explicit" - computedNumberOfChannels is the exact value as specified by the channelCount.

channelInterpretation #


channelInterpretation determines how individual channels will be treated when up-mixing and down-mixing connections to any inputs to the node. The default value is "speakers".

context #


The context belonging to the node.

debug #


Set this debug flag to log all events that happen in this class.

detune #

Signal<"cents" >

The detune value in cents (100th of a semitone).

const osc = new Tone.PulseOscillator("F3").toDestination().start();
// pitch it 1 octave = 12 semitones = 1200 cents
osc.detune.setValueAtTime(1200, + 0.5);
osc.detune.linearRampToValueAtTime(0, + 1);
osc.stop( + 1.5);

disposed #

readonly boolean

Indicates if the instance was disposed. 'Disposing' an instance means that all of the Web Audio nodes that were created for the instance are disconnected and freed for garbage collection.

frequency #

Signal<"frequency" >

The frequency value of the oscillator

const osc = new Tone.FMOscillator("Bb4").toDestination().start();
osc.frequency.rampTo("D2", 3);

harmonicity #

Signal<"positive" >

Harmonicity is the frequency ratio between the carrier and the modulator oscillators. A harmonicity of 1 gives both oscillators the same frequency. Harmonicity = 2 means a change of an octave.

const fmOsc = new Tone.FMOscillator("D2").toDestination().start();
// pitch the modulator an octave below carrier
fmOsc.harmonicity.value = 0.5;

input #


Sources have no inputs

modulationIndex #

Signal<"positive" >

The modulation index which is in essence the depth or amount of the modulation. In other terms it is the ratio of the frequency of the modulating signal (mf) to the amplitude of the modulating signal (ma) -- as in ma/mf.

modulationType #


The type of the modulator oscillator

mute #


Mute the output.

const osc = new Tone.Oscillator().toDestination().start();
// mute the output
osc.mute = true;

numberOfInputs #

readonly number

The number of inputs feeding into the AudioNode. For source nodes, this will be 0.

const node = new Tone.Gain();

numberOfOutputs #

readonly number

The number of outputs of the AudioNode.

const node = new Tone.Gain();

onstop #


The callback to invoke when the source is stopped.

output #


The output note

partialCount #


'partialCount' offers an alternative way to set the number of used partials. When partialCount is 0, the maximum number of partials are used when representing the waveform using the periodicWave. When 'partials' is set, this value is not settable, but equals the length of the partials array. A square wave wave is composed of only odd harmonics up through the harmonic series. Partial count can limit the number of harmonics which are used to generate the waveform.

const osc = new Tone.Oscillator("C3", "square").toDestination().start();
osc.partialCount = 1;
setInterval(() => {
}, 500);

partials #

number []

The partials describes the relative amplitude of each of the harmonics of the oscillator. The first value in the array is the first harmonic (i.e. the fundamental frequency), the second harmonic is an octave up, the third harmonic is an octave and a fifth, etc. The resulting oscillator output is composed of a sine tone at the relative amplitude at each of the harmonic intervals.

const osc = new Tone.Oscillator("F3").toDestination().start();
setInterval(() => {
	// generate 8 random partials
	osc.partials = new Array(8).map(() => Math.random());
}, 1000);

phase #


The phase is the starting position within the oscillator's cycle. For example a phase of 180 would start halfway through the oscillator's cycle.

return Tone.Offline(() => {
	const osc = new Tone.Oscillator({
		frequency: 20,
		phase: 90
}, 0.1, 1);

sampleTime #

readonly Seconds

The duration in seconds of one sample.


state #

readonly BasicPlaybackState

Returns the playback state of the source, either "started" or "stopped".

const player = new Tone.Player("", () => {

type #


The oscillator's type. Also capable of setting the first x number of partials of the oscillator. For example: "sine4" would set be the first 4 partials of the sine wave and "triangle8" would set the first 8 partials of the triangle wave.

return Tone.Offline(() => {
	const osc = new Tone.Oscillator().toDestination().start();
	osc.type = "sine2";
}, 0.1, 1);

static version #


The version number semver

volume #

Param<"decibels" >

The volume of the output in decibels.

const source = new Tone.PWMOscillator().toDestination();
source.volume.value = -6;


asArray #

Returns an array of values which represents the waveform.

asArray (
length= 1024:number
) => Promise<Float32Array >

chain #

Connect the output of this node to the rest of the nodes in series.

const player = new Tone.Player("");
player.autostart = true;
const filter = new Tone.AutoFilter(4).start();
const distortion = new Tone.Distortion(0.5);
// connect the player to the filter, distortion and then to the master output
player.chain(filter, distortion, Tone.Destination);
chain (
...nodes:InputNode []
) => this

connect #

connect the output of a ToneAudioNode to an AudioParam, AudioNode, or ToneAudioNode

connect (
destination:InputNode ,

The output to connect to

outputNum= 0:number ,

The output to connect from

inputNum= 0:number

The input to connect to

) => this

disconnect #

disconnect the output

disconnect (
destination?:InputNode ,
outputNum= 0:number ,
inputNum= 0:number
) => this

dispose #

Clean up.

dispose ( ) => this

fan #

connect the output of this node to the rest of the nodes in parallel.

const player = new Tone.Player("");
player.autostart = true;
const pitchShift = new Tone.PitchShift(4).toDestination();
const filter = new Tone.Filter("G5").toDestination();
// connect a node to the pitch shift and filter in parallel, filter);
fan (
...nodes:InputNode []
) => this

get #

Get the object's attributes.

const osc = new Tone.Oscillator();
get ( ) => FMOscillatorOptions

static getDefaults #

Returns all of the default options belonging to the class.

getDefaults ( ) => FMOscillatorOptions

immediate #

Return the current time of the Context clock without any lookAhead.

setInterval(() => {
}, 100);
immediate ( ) => Seconds

now #

Return the current time of the Context clock plus the lookAhead.

setInterval(() => {
}, 100);
now ( ) => Seconds

restart #

Restart the source.

restart (
time?:Time ,
offset?:Time ,
) => this

set #

Set multiple properties at once with an object.

const filter = new Tone.Filter();
// set values using an object
	frequency: 300,
	type: "highpass"
set ( ) => this

start #

Start the source at the specified time. If no time is given, start the source now.

const source = new Tone.Oscillator().toDestination();
source.start("+0.5"); // starts the source 0.5 seconds from now
start (
time?:Time ,

When the source should be started.

offset?:Time ,
) => this

stop #

Stop the source at the specified time. If no time is given, stop the source now.

const source = new Tone.Oscillator().toDestination();
source.stop("+0.5"); // stops the source 0.5 seconds from now
stop (

When the source should be stopped.

) => this

sync #

Sync the source to the Transport so that all subsequent calls to start and stop are synced to the TransportTime instead of the AudioContext time.

const osc = new Tone.Oscillator().toDestination();
// sync the source so that it plays between 0 and 0.3 on the Transport's timeline
// start the transport.
// set it to loop once a second
Tone.Transport.loop = true;
Tone.Transport.loopEnd = 1;
sync ( ) => this

toDestination #

Connect the output to the context's destination node.

const osc = new Tone.Oscillator("C2").start();
toDestination ( ) => this

toFrequency #

Convert the input to a frequency number

const gain = new Tone.Gain();
toFrequency (
) => Hertz


Connect the output to the context's destination node. See toDestination

toMaster ( ) => this

toSeconds #

Convert the incoming time to seconds

const gain = new Tone.Gain();
toSeconds (
) => Seconds

toString #

Convert the class to a string

const osc = new Tone.Oscillator();
toString ( ) => string

toTicks #

Convert the input time into ticks

const gain = new Tone.Gain();
toTicks (
time?:Time | TimeClass
) => Ticks

unsync #

Unsync the source to the Transport. See Source.sync

unsync ( ) => this