Make Music That Moves: The LFO Modulator

Have you ever heard a song where the volume slowly swells up and down? Or a sound that wobbles like a wobbly jelly? That is called modulation. It makes music feel alive. In Fortnite Creative, we use a special tool called the LFO Modulator. It acts like a remote control for sounds. It changes settings automatically. You do not need to touch anything. The sound does it for you. Let us build a wobbly bass sound together.

What You'll Learn

• What an LFO Modulator is.
• How to connect it to a sound device.
• How to make a sound wobble or pulse.

How It Works

Think of the LFO Modulator as a magic knob. Imagine you are playing a video game. You find a music box. The music box has a volume knob. Usually, the knob stays still. But with the LFO, the knob turns by itself. It turns left, then right, then left again. This creates a pattern.

The word "LFO" stands for Low-Frequency Oscillator. That sounds hard. Let us break it down. An oscillator is just something that goes back and forth. Like a swing. Low frequency means it moves slowly. So, the LFO moves a setting slowly and repeatedly.

You can connect this magic knob to other devices. These are called Patchwork devices. Patchwork is a system for making music and sound in Fortnite. You can connect the LFO to a speaker. You can connect it to a bass drum. You can even connect it to a light! It changes the value of whatever it is connected to.

Let us make a sound that breathes. We will make a bass sound that gets louder and softer. This is called a "swell." It is very cool for spooky islands or calm forests.

Let's Build It

We will build a simple setup. We need two devices. First, we need a sound source. Second, we need the LFO to control it.

Here is how to set it up in the UEFN editor.

1. Place a Patchwork Speaker on your island.
2. Place a Patchwork LFO Modulator next to it.
3. Connect the LFO to the Speaker.

Let us look at the code-like logic behind this. In Verse, we think in terms of devices and connections.

using { /Fortnite.com/Devices }
using { /Fortnite.com/Devices/Patchwork }
using { /Verse.org/Simulation }

# This Verse device holds references to the Patchwork devices
# placed in the UEFN editor and wired together there.
patchwork_controller := class(creative_device):

    # This is the sound device. It makes the noise.
    # Drag your Patchwork Speaker into this slot in the editor.
    @editable
    Speaker : audio_player_device = audio_player_device{}

    # This is the magic knob. It changes values.
    # Drag your Patchwork LFO Modulator into this slot in the editor.
    @editable
    LFO : lfo_modulator_device = lfo_modulator_device{}

    OnBegin<override>()<suspends> : void =
        # Connect the LFO to the Speaker's volume.
        # Now the volume will change on its own!
        # note: Patchwork signal routing is primarily done in the
        # UEFN editor's Patchwork panel by drawing cables between
        # the LFO output port and the Speaker volume input port.
        # The code below sets properties on each device to configure
        # the swell behaviour after the editor cable is in place.

        # Set the LFO speed.
        # Low speed = slow swell. High speed = fast wobble.
        # Rate of 0.5 means one cycle every two seconds.
        LFO.SetFrequency(0.5)

        # Start the speaker so it plays continuously.
        Speaker.Play()```

Let us walk through what each part does. The speaker is the worker. It plays the sound. The LFO is the boss. It tells the speaker what to do. The cable you draw in the editor is the wire. It links the two devices. When the LFO moves, the speaker hears it. The `SetRate` line sets the speed. A rate of 0.5 means one cycle every two seconds. Try changing this number. See what happens.

You can also change the shape of the wave. The LFO can go in a straight line. It can go in a triangle. It can go in a smooth curve. This is called the waveform. A sine wave is smooth. A square wave is sharp. Try different shapes. They sound very different.

## Try It Yourself

Now it is your turn to create. You have the tools. You have the knowledge. Here is your challenge.

**Challenge:** Make a sound that clicks fast.

**Hint:** Try connecting the LFO to a different setting on the speaker. Maybe the pitch? Or maybe try a higher rate number. A higher number means faster movement. What happens if you use a square wave?

## Recap

You learned how to use the LFO Modulator. It is a magic knob for sounds. It changes settings automatically. You can connect it to speakers or lights. It makes your island feel alive. Keep experimenting. Try new shapes and speeds. You are now a sound designer!

## References

- https://dev.epicgames.com/documentation/en-us/fortnite/using-patchwork-lfo-modulator-devices-in-fortnite-creative
- https://dev.epicgames.com/documentation/en-us/fortnite-creative/using-patchwork-lfo-modulator-devices-in-fortnite-creative
- https://dev.epicgames.com/documentation/en-us/fortnite/getting-started-with-patchwork-in-fortnite-creative
- https://dev.epicgames.com/documentation/en-us/fortnite/fortnite-glossary
- https://dev.epicgames.com/documentation/en-us/fortnite-creative/build-patchwork-x-yacht-heist-1-adaptive-soundtrack-in-fortnite-creative