Module JSON Schema

RMT Compose modules are saved as JSON files. This document describes the complete schema.

Top-Level Structure

{
  "baseNote": { ... },
  "notes": [ ... ]
}

Field	Type	Description
baseNote	object	Reference note with default values
notes	array	Array of note objects

Expression Formats

RMT Compose supports two expression formats in JSON files:

DSL Format (Recommended)

Concise, mathematical notation:

{
  "baseNote": {
    "frequency": "440",
    "tempo": "120"
  },
  "notes": [
    {
      "id": 1,
      "frequency": "base.f * (3/2)",
      "startTime": "base.t",
      "duration": "beat(base)"
    }
  ]
}

Legacy Format

JavaScript-like method chaining (still fully supported):

{
  "baseNote": {
    "frequency": "new Fraction(440)",
    "tempo": "new Fraction(120)"
  },
  "notes": [
    {
      "id": 1,
      "frequency": "module.baseNote.getVariable('frequency').mul(new Fraction(3, 2))",
      "startTime": "module.baseNote.getVariable('startTime')",
      "duration": "new Fraction(60).div(module.findTempo(module.baseNote))"
    }
  ]
}

Both formats can be mixed within the same file - each expression is detected independently.

BaseNote Object

DSL Format

{
  "baseNote": {
    "frequency": "440",
    "startTime": "0",
    "duration": "1",
    "tempo": "120",
    "beatsPerMeasure": "4"
  }
}

Legacy Format

{
  "baseNote": {
    "frequency": "new Fraction(440)",
    "startTime": "new Fraction(0)",
    "duration": "new Fraction(1)",
    "tempo": "new Fraction(120)",
    "beatsPerMeasure": "new Fraction(4)"
  }
}

Property	Type	Default	Description
frequency	string	"440"	Base frequency in Hz
startTime	string	"0"	Start time reference
duration	string	"1"	Default duration
tempo	string	"60"	Tempo in BPM
beatsPerMeasure	string	"4"	Time signature numerator

Note Object

DSL Format

{
  "id": 1,
  "frequency": "base.f * (3/2)",
  "startTime": "base.t",
  "duration": "beat(base)",
  "color": "#4a90d9",
  "instrument": "sine-wave"
}

Legacy Format

{
  "id": 1,
  "frequency": "module.baseNote.getVariable('frequency').mul(new Fraction(3, 2))",
  "startTime": "module.baseNote.getVariable('startTime')",
  "duration": "new Fraction(60).div(module.findTempo(module.baseNote))",
  "color": "#4a90d9",
  "instrument": "sine-wave"
}

Property	Type	Required	Description
id	number	Yes	Unique note identifier (positive integer)
frequency	string	No	Frequency expression
startTime	string	No	Start time expression
duration	string	No	Duration expression
tempo	string	No	Tempo override (rare)
beatsPerMeasure	string	No	Time signature override (rare)
color	string	No	CSS color for visualization
instrument	string	No	Instrument name

Expression Syntax Quick Reference

DSL Syntax

440               # Integer
(3/2)             # Fraction
[1].f             # Note 1 frequency
base.t            # BaseNote startTime
a + b             # Add
a * b             # Multiply
2^(1/12)          # Power
tempo(base)       # Get tempo
measure([1])      # Get measure length
beat(base)        # Get beat duration

Legacy Syntax

new Fraction(440)
new Fraction(3, 2)
module.getNoteById(1).getVariable('frequency')
module.baseNote.getVariable('startTime')
a.add(b)
a.mul(b)
new Fraction(2).pow(new Fraction(1, 12))
module.findTempo(module.baseNote)
module.findMeasureLength(module.getNoteById(1))
new Fraction(60).div(module.findTempo(module.baseNote))

Complete Example (DSL Format)

{
  "baseNote": {
    "frequency": "440",
    "startTime": "0",
    "duration": "1",
    "tempo": "120",
    "beatsPerMeasure": "4"
  },
  "notes": [
    {
      "id": 1,
      "frequency": "base.f",
      "startTime": "base.t",
      "duration": "beat(base)",
      "color": "#4a90d9"
    },
    {
      "id": 2,
      "frequency": "base.f * (5/4)",
      "startTime": "[1].t + [1].d",
      "duration": "beat(base)",
      "color": "#e74c3c"
    },
    {
      "id": 3,
      "frequency": "base.f * (3/2)",
      "startTime": "[2].t + [2].d",
      "duration": "beat(base)",
      "color": "#2ecc71"
    }
  ]
}

This creates a simple C-E-G arpeggio using just intonation ratios.

Instruments

Built-in instrument names:

Name	Type	Description
sine-wave	Synth	Pure sine wave
square-wave	Synth	Square wave
sawtooth-wave	Synth	Sawtooth wave
triangle-wave	Synth	Triangle wave
organ	Synth	Organ with harmonics
vibraphone	Synth	Vibraphone with vibrato
piano	Sample	Piano samples
violin	Sample	Violin samples

File Extension

RMT Compose modules use the .json extension. When saving, the suggested filename is module.json.

Validation

When loading a module:

1. ID uniqueness: All note IDs must be unique
2. ID validity: Referenced note IDs must exist
3. No circular dependencies: Expressions cannot form dependency cycles
4. Valid expressions: All expression strings must be syntactically valid (DSL or legacy)

Format Detection

The loader automatically detects whether each expression uses DSL or legacy format:

• DSL indicators: [id]., base., (n/n), tempo(, measure(, beat(
• Legacy indicators: new Fraction, module., .getVariable(, .mul(, .div(
• Plain numbers (e.g., 440) are valid in both formats

Binary Format (Internal)

Internally, expressions are compiled to binary bytecode for efficient evaluation. The JSON format stores the human-readable source; bytecode is generated at load time.

See Also

• Saving Modules - How to save
• Loading Modules - How to load
• Expression Syntax - Complete expression reference