In this tutorial, you’ll learn how to create procedural music using MetaSounds. You’ll create procedurally-generated background music for your adventure game.
MetaSounds is a high-performance audio system that can generate sound sources using a node-based system, similar to the Blueprint Visual Scripting system.
Before You Begin
Make sure you understand these topics covered in the Unreal Engine for New Users documentation:
Blueprint basics, such as adding and connecting nodes.
Create Procedural Music with MetaSounds
You’ll start by creating a MetaSound asset. Follow these steps:
Go to the Content Browser and navigate to the Content > AdventureGame > Artist > Audio folder.
In the Audio folder, create a new folder named Music.
Right-click inside the Music folder and select Audio > MetaSound Source.
Name this asset
MS_BGM, which stands for MetaSound Background Music.Open the asset.
The asset opens in the MetaSound Editor. In the new window, you will see three nodes in the graph – Input, Output On Finished, and Input Out Mono.
The Input trigger is executed when this audio source is played. A MetaSound always begins with an Input.
The Output On Finished trigger is executed to stop the source from playing. If you’re stopping the audio from somewhere else, like a blueprint, you don’t have to use this node to stop the audio source from playing. In this case, you’ll use a blueprint to start and stop the audio, so you won’t have to use this node.
The Output Out Mono node represents the final audio output of the MetaSound graph, routing all upstream audio signals into a single-channel (mono) output. Any nodes connected to it are effectively mixed down and sent to the engine as the sound’s output.
Set Music Tempo and Rhythm
First, you’ll create the nodes to set the tempo and rhythm of the music. Follow these steps:
Drag the Input node’s pin and add a Trigger Repeat node.
On the Trigger Repeat node, drag the Period pin and add a BPM To Seconds node. Set the Divisions of Whole Note to 16.
On the BPM To Seconds node, drag the BPM pin and select Promote to Graph Input.
In the Members panel in the top-left corner of the screen, rename Input from BPM to Note In.
In the Details panel, change the Default Value of the Note In node to 60. You can also change this value at the bottom of the node.
From the Trigger Repeat node, drag the RepeatOut pin and add a new Trigger Counter node.
Select the Trigger Counter node and set the Reset Count to 8.
This section sets the tempo and rhythm. Additionally, you can highlight all four nodes you added – Trigger Counter, Trigger Repeat, BPM To Seconds, and Input – and press C to add a comment box that contains all of the nodes. Name this comment box Tempo and Rhythm.
Generate a Melody
Next, you’ll create the functionality that generates the melody using the tempo and rhythm you defined. Follow these steps:
From the Trigger Counter node:
Drag the On Trigger pin and add a Random Get (Float:Array) node.
Drag the Trigger Counter node’s On Reset pin and connect it to the Random Get node’s Reset pin.
From the Random Get node, drag the In Array pin and add a Scale to Note Array node.
From the Scale to Note Array node, drag the Scale Degrees pin and add select Promote to Graph Input and name it Scale.
From the Random Get node, drag the Seed pin and add a Random (Int) node.
From the Random (Int) node, drag the Next pin and connect it to the Trigger Counter node’s On Reset pin.
This section generates the melody. Once again, you can highlight all of the new nodes and add a comment box called Melody Generation.
Synthesize the Melody
Next, you’ll shape how that melody actually sounds by creating the synthesis. This means turning the generated melody notes into audible sound. Follow these steps:
On the Random Get node, drag the Value pin and add an Add (Float) node.
On the Add node, change the second input pin’s value from 0 to 48.
From the Add node, drag the exec pin and add a MIDI To Frequency (Float) node.
From the MIDI To Frequency (Float) node, drag the Out Frequency pin and add a Sine node.
From the Sine node, drag the Audio output pin and add an Add (Audio) node.
You’ll add one more Sine node that connects to this Add node. So, from the Add node, drag the other input pin and add a Sine node.
On the new Sine node, drag the Frequency pin and add a MIDI To Frequency (Float) node.
From the MIDI To Frequency node, drag the MIDI In pin and add an Add (Float) node.
On the Add node:
Connect the first input pin to the Add node that is connected to the first Sine node.
Drag the second input pin and select Promote to Graph Input. Name it Detune.
Select the Detune input and in the Details panel, change its Range to 0 and 12.
In the Details panel, change the Default value to 12.
Now, you’ve synthesized the melody that will be generated. You can once again add a comment box for this new section and name it Synthesis.
Shape the Sound With an Envelope
Next, you’ll add an envelope to shape how the sound evolves over time, controlling its start, sustain, and fade-out for a more natural result.
To add an envelope, follow these steps:
Scroll to the melody generation section you created previously (if you added a comment box, it should be named Melody Generation). From the Random Get (Float:Array) node, drag the On Next pin and add an AD Envelope (Audio) node. Move this new node after the two Sine nodes you added in the synthesis section.
From this node, drag the Out Envelope pin and add a Multiply (Audio) node.
From this Multiply node, drag the second input pin and connect it to the output pin of the Add (Audio) node that you connected the two Sine nodes to.
On the AD Envelope (Audio) node, change the Decay Time to 0.2.
From the Multiply (Audio) node, drag the output pin and connect it to the Output Out Mono node that was already in the MetaSound Source.
Now, press the Play button in the toolbar near the top of the MetaSound Source window. It will continuously play procedurally-generated music.
To learn more about crafting procedural music in Unreal Engine, see the Creating Procedural Music with MetaSounds page.
Play the Music In-Game With Blueprints
Before moving on, you’ll create a Blueprint that plays the background music in the level.
Since this blueprint will be added to the level but doesn’t have a visual representation, you’ll add a Billboard component to the blueprint. This component adds a 2D sprite that makes it visible in the editor so you can find it while editing your level, but it won’t be visible in the game.
To create the background music blueprint, follow these steps:
Go to the Content Browser and navigate to Content > AdventureGame > Artist > Audio > Music.
Right-click and create a new Blueprint Class that derives from the Actor parent class. Name this BP_BGM, which stands for Blueprint Background Music.
In the Components panel, click Add and add a Billboard component. In the Details panel, you can see that the Sprite is set to S_Actor by default. You can change the sprite or leave it as is.
Go to the EventGraph tab to start building the functionality.
Drag from the Event BeginPlay node and add a Branch node.
From the Branch node, drag the Condition pin and select Promote to Variable. Name this variable Active. This variable will be used to determine if this audio source is active or not.
In the Variables list in the My Blueprints panel, click the eye icon next to the Active variable so the eye is open, making it public and editable in the level editor.
Compile the blueprint, use the Details panel to ensure the Active variable’s Default Value is true (enabled).
From the Branch node, drag the True pin and add a Play Sound 2D node.
On the Play Sound 2D node, use the dropdown to set the Sound pin to MS_BGM.
From the Play Sound 2D node, click the down arrow to expand the node options. Drag the Volume Multiplier pin and select Promote to Variable.
Click the variable’s eye icon to make it public and editable, Compile the blueprint, and change its default value to 0.5.
Save and compile your blueprint.
The “2D” in the Play Sound 2D node indicates that the sound will play independently of the player’s position in the level. In other words, it’s not spatialized in 3D space so distance and direction don’t affect how the player hears it.
Test Your Music In-Game
You can now go back to the level editor and add the BP_BGM blueprint into your level.
Select the BP_BGM actor in the level, and in the Details panel, make sure that the two variables you added are correctly set up: Active should be toggled on, and the Volume Multiplier should be set to 0.5.
You can try different values for the Volume Multiplier and see what works best for your use case. Since this is the background music, you might want to have its volume set to lower values to keep it subtle.
Now, play the game. You should hear the music that you created play in the background!
Next Up
In the next module you will learn how to add dynamic footstep sound effects to your player character, that playback different sounds depending on the type of floor the character is currently moving across.
