MetaSounds DSP — Node Graphs & Signal Design

Design MetaSounds audio graphs: choose nodes, wire signal chains, configure DSP parameters, and generate Builder API command sequences.

Data Types

Audio, Trigger, Float, Int32, Bool, Time, String, WaveAsset, UObject, Enum (+ Array variants)

Type rules: Audio-rate cannot connect to Float. Use correct node variant (e.g., Multiply (Audio) vs Multiply (Float)).

Asset Types

Interfaces

• MetaSound — Standard audio output
• UE.Source.OneShot — OnPlay trigger in, OnFinished trigger out
• UE.Attenuation — Distance input for volume falloff
• UE.Spatialization — Azimuth/Elevation for 3D positioning

Node Categories (144 nodes, 20 categories)

Generators

Sine, Saw, Square, Triangle, Noise, LFO, Additive Synth, SuperOscillator, WaveTable, Perlin Noise

Wave Players

Wave Player (mono), Stereo Wave Player, with loop/pitch shift/concatenation

Envelopes

AD Envelope (Audio-rate), AD Envelope (Float), ADSR Envelope, Crossfade, WaveTable Envelope

Filters

Biquad Filter, State Variable Filter, Dynamic Filter, Ladder Filter, One-Pole HPF, One-Pole LPF, Band Splitter, Bitcrusher

Delays & Time

Delay, Stereo Delay, Pitch Shift, Diffuser, Grain Delay, Flanger

Dynamics

Compressor, Limiter

Math (Audio)

Add, Subtract, Multiply, Mix — all have Primary Operand + Operand pins

Math (Float)

Add, Subtract, Multiply, Divide, Modulo, Map Range, Clamp, InterpTo, Linear To Log Frequency

Triggers

Accumulate, Any, Compare, Control, Counter, Delay, Filter, Gate, Once, OnThreshold, OnValueChange, Pipe, Repeat, Route, Sequence

Spatialization

ITD Panner, Stereo Panner, Mid-Side Encode/Decode, Doppler Pitch Shift

Music

Frequency↔MIDI, MIDI Quantizer, Scale to Note Array, BPM to Seconds, Metronome, Quartz Clock

Effects

Plate Reverb, Ring Modulator, WaveShaper, Chorus, Phaser

Utility

Crossfade, Envelope Follower, Wave Writer, Random Get, Trigger On Threshold

SIDKIT (Custom)

SID Oscillator, SID Envelope, SID Filter, SID Voice, SID Chip

Signal Flow Patterns

Basic: Generator → Envelope → Output

Sine → Multiply(Audio) × AD Envelope → Out Mono

Subtractive: Osc → Filter → Amp → Output

Saw → Biquad Filter(LP) → Multiply × ADSR → Out Mono
         ↑ Cutoff Frequency

Additive: Multiple Oscs → Mix → Output

Sine(f) + Sine(2f) + Sine(3f) → Add → Multiply × Envelope → Out

Triggered: Event → Sample Player → Processing

OnPlay → Wave Player → Biquad Filter → Compressor → Out
                         ↑ Pitch Shift for variation

Modulated: LFO → Parameter Control

LFO → Map Range(0-1 → 200-2000) → Biquad Filter Cutoff

Key Pin Names (Authoritative)

Full reference: scripts/ms_node_specs.json (93 nodes, 464 pins from Epic docs)

Builder API Functions (68+)

Core

CreateSourceBuilder, CreatePatchBuilder, AddNode, FindNodeInputHandle, FindNodeOutputHandle, ConnectNodes, SetNodeInputDefault, Audition, BuildToAsset

Graph I/O

AddGraphInput, AddGraphOutput, RemoveGraphInput, RemoveGraphOutput, GetGraphInputNames

Interfaces

AddInterface, RemoveInterface, IsInterfaceDeclared

Variables (UE 5.7+)

AddGraphVariable, AddVariableGetNode, AddVariableSetNode, AddVariableGetDelayedNode

Presets

ConvertToPreset, ConvertFromPreset

Live Updates

SetLiveUpdatesEnabled

Templates Available (22 JSON)

Templates at: src/ue_audio_mcp/templates/

Graph JSON Spec

{
  "type": "source",
  "interface": "MetaSound",
  "nodes": [
    {"id": "osc1", "class": "Sine", "defaults": {"Frequency": 440.0}},
    {"id": "env1", "class": "AD Envelope", "defaults": {"Attack Time": 0.01, "Decay Time": 0.5}}
  ],
  "connections": [
    {"from": "osc1:Audio", "to": "env1:In"}
  ],
  "inputs": [
    {"name": "Frequency", "type": "Float", "target": "osc1:Frequency"}
  ],
  "outputs": [
    {"name": "Out Mono", "type": "Audio", "source": "env1:Out Envelope"}
  ]
}

Validated by 7-stage validator: required fields, asset_type, interfaces, node types, pin existence, type compatibility, required inputs, interface completeness.

Design Guidelines

1. Choose asset type: Source (playable) or Patch (reusable subgraph)
2. Select interface: MetaSound (general), OneShot (fire-and-forget)
3. Design signal flow: Generator → Processing → Envelope → Mixing → Output
4. Expose parameters Blueprint needs to control as graph inputs
5. Use SetNodeLocation() for editor layout visibility
6. Validate with ms_validate_graph before sending to Builder API
7. Consider AudioLink if routing to Wwise for mixing

Gotchas

• AD Envelope (Float) for modulation chains, AD Envelope (Audio) for amplitude
• InterpTo requires Current default value
• Float→Audio connections are invalid — use Biquad Filter Bandwidth, not Multiply Audio
• Dynamic Filter needs Audio-rate cutoff input; use Biquad for Float cutoff
• Pin names from Epic docs may use shorthand — always verify against ms_node_specs.json
• Node class names: use display names from knowledge DB, or full Namespace::Name::Variant for direct lookup

Source Files

• Node catalogue: src/ue_audio_mcp/knowledge/metasound_nodes.py (144 nodes, 798 pins)
• Templates: src/ue_audio_mcp/templates/ (22 JSON graphs)
• Graph schema: src/ue_audio_mcp/knowledge/graph_schema.py
• Builder tools: src/ue_audio_mcp/tools/metasounds.py
• Scraped pins: scripts/ms_node_specs.json

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