metasounds

🧠 Brains complement: IF an unreal-engine-skills-manager tool (external MCP) exists in this session, call it with {action: "load", skill: "audio-and-metasounds"} for UE domain knowledge on this topic — correct APIs, architecture, best practices — and treat it as the rubric for any review / "best practices" question. If no such tool is available (e.g. running under Claude Code or Codex without that MCP), skip this line entirely and proceed with this skill alone — do NOT attempt the call.

MetaSound Service Skill

Use this skill to create and edit MetaSound Source assets via Python.

import unreal
ms = unreal.MetaSoundService()

Key Concepts

• MetaSound Source — a procedural audio asset (UMetaSoundSource) defined by a node graph. It replaces SoundCue for runtime-parameterisable sounds.
• Node — a DSP processing block (Sine oscillator, Gain, Delay, etc.). Nodes have named input pins and output pins with associated DataTypes.
• NodeId — a GUID string returned by add_node. Pass it to connect, remove, set_default, etc.
• Graph I/O — add_graph_input / add_graph_output expose values at the asset level (settable at runtime via Set Float Parameter, etc.).
• Standard interface — every Source created by this service comes pre-wired with:
  • On Play (Trigger output) — fires when the sound starts
  • On Finished (Trigger input) — call to stop the sound
  • Audio:0 (Audio input on the graph output node) — connect your audio signal here

---

Workflow

1 — Discover available nodes

# List all nodes whose class name or display name contains "Sine"
nodes = ms.list_available_nodes("Sine")
for n in nodes:
    print(n.full_class_name, "  inputs:", n.inputs, "  outputs:", n.outputs)

2 — Create a MetaSound

r = ms.create_meta_sound("/Game/Audio", "MS_SineLoop", "Mono")
asset_path = r.asset_path   # "/Game/Audio/MS_SineLoop"

3 — Find the built-in interface node IDs

all_nodes = ms.list_nodes(asset_path)
for n in all_nodes:
    print(n.node_id, n.node_title, n.inputs, n.outputs)

# IMPORTANT: A MetaSound Source has MULTIPLE nodes with title "Output" —
# one per interface pin group (e.g. "On Finished" Trigger, "Out Mono" Audio).
# You MUST filter by the node whose inputs contain an Audio-type pin.
# Pin strings are "VertexName:TypeName" — the TypeName suffix after the last colon.
audio_out_node = next(
    n for n in all_nodes
    if n.node_title == "Output" and any(p.endswith(":Audio") for p in n.inputs)
)
audio_out_id = audio_out_node.node_id
# Drop the last :TypeName suffix to get the raw vertex name for connect_nodes
audio_in_pin = ":".join(audio_out_node.inputs[0].split(":")[:-1])  # "UE.OutputFormat.Mono.Audio:0"

# Input node — filter by class_name "Input.Trigger" to avoid matching graph input nodes
# (graph inputs also appear as "Input" nodes but with class "Input.Float", "Input.Bool", etc.)
input_node = next(n for n in all_nodes if n.class_name == "Input.Trigger")
input_node_id = input_node.node_id
on_play_pin = ":".join(input_node.outputs[0].split(":")[:-1])  # "UE.Source.OnPlay"