pxt-microbit/docs/reference/music/create-sound-expression.md

micro:bit target for Microsoft MakeCode (PXT)

# create Sound Expression

Create a sound expression object for a sound effect.

```sig
music.createSoundExpression(WaveShape.Sine, 2000, 0, 1023, 0, 500, SoundExpressionEffect.None, InterpolationCurve.Linear)
```

A sound expression is set of parameters that describe a **[Sound](/types/sound)** that will last for some amount of time. These parameters specify a base waveform, frequency range, sound volume, and effects. Sound data is created as a [Sound](/types/sound) object and can then be [played](/reference/music/play) to the speaker, headphones, or at an output pin.

## Parameters

* **waveShape**: the primary shape of the waveform:
>* `sine`: sine wave shape
>* `sawtooth`: sawtooth wave shape
>* `triangle`: triangle wave shape
>* `square`: square wave shape
>* `noise`: random noise generated wave shape
* **startFrequency**: a [number](/types/number) that is the frequency of the waveform when the sound expression starts.
* **endFrequency**: a [number](/types/number) that is the frequency of the waveform when the sound expression stops.
* **startVolume**: a [number](/types/number) the initial volume of the sound expression.
* **endVolume**: a [number](/types/number) the ending volume of the sound expression.
* **duration**: a [number](/types/number) the duration in milliseconds of the sound expression.
* **effect**: an effect to add to the waveform. These are:
>* `tremolo`: add slight changes in volume of the sound expression.
>* `vibrato`: add slight changes in frequency to the sound expression.
>* `warble`: a combination of the `tremolo` and `vibrato` effects.
* **interpolation**: controls the rate of frequency change in the sound expression.
>* `linear`: the change in frequency is constant for the duration of the sound.
>* `curve`: the change in frequency is faster at the beginning of the sound and slows toward the end.
>* `logarithmic`: the change in frequency is rapid during the very first part of the sound.

## Returns

* a [sound](/types/sound) expression with the the desired sound effect parameters.

## Examples

### Sine wave sound

Create a sound expression and assign it to a variable. Play the sound for the sound expression.

```blocks
let mySound = music.createSoundExpression(WaveShape.Sine, 2000, 0, 1023, 0, 500, SoundExpressionEffect.None, InterpolationCurve.Linear)
music.play(mySound, music.PlaybackMode.UntilDone)
```

### Complex waveform sound

Create a `triangle` wave sound expression with `vibrato` and a `curve` interpolation. Play the sound until it finishes.

```typescript
let mySound = music.createSoundExpression(
    WaveShape.Triangle,
    1000,
    2700,
    255,
    255,
    500,
    SoundExpressionEffect.Vibrato,
    InterpolationCurve.Curve
    )
music.play(mySound, music.PlaybackMode.UntilDone)
```

## See also

[play](/reference/music/play)