Song Spec Format

Declarative specification format for XM/IT tracker modules. The spec defines instruments, patterns, and arrangement - the parser handles all binary generation.

All specs use .spec.py extension. The containing folder and dict name (SONG) identify the type.

Quick Start

# .studio/specs/music/theme.spec.py
SONG = {
    "song": {
        "name": "theme",
        "format": "xm",
        "bpm": 120,
        "speed": 6,
        "channels": 4,

        "instruments": [
            {"ref": "../instruments/kick.spec.py"},
            {"ref": "../instruments/bass.spec.py"}
        ],

        "patterns": {
            "main": {
                "rows": 64,
                "notes": {
                    0: [{"row": 0, "note": "C-3", "inst": 0, "vol": 64}],
                    1: [{"row": 0, "note": "C-2", "inst": 1, "vol": 64}]
                }
            }
        },

        "arrangement": [{"pattern": "main", "repeat": 4}],
        "restart_position": 0
    }
}

Generate:

python .studio/generate.py --only music

Spec Structure Overview

Section	Purpose
name, title	Module identification
format	Output format: "xm" or "it"
bpm, speed	Tempo (BPM, ticks per row)
channels	Channel count (XM max 32, IT max 64)
instruments	Instrument definitions (ref, inline, or WAV)
patterns	Named patterns with row-based notes
arrangement	Pattern playback order
automation	Procedural effects (volume fades, tempo changes)

Instruments

Three loading modes:

External Reference (Recommended)

{"ref": "../instruments/kick.spec.py"}

Best for reusable instruments defined in .studio/specs/instruments/.

Inline Synthesis

{
    "name": "bass",
    "synthesis": {"type": "karplus_strong", "damping": 0.994},
    "envelope": {"attack": 0.01, "decay": 0.4},
    "base_note": "C2",
    "output": {"duration": 1.5}
}

Self-contained synthesis spec. Good for one-off instruments.

WAV File

{"wav": "samples/piano.wav", "name": "piano"}

Load pre-recorded sample. For complex sounds hard to synthesize.

Pattern Notes

Row-based note placement (native to tracker format):

"patterns": {
    "verse": {
        "rows": 64,
        "notes": {
            0: [  # Channel 0 (kick)
                {"row": 0, "note": "C-3", "inst": 0, "vol": 64},
                {"row": 16, "note": "C-3", "inst": 0, "vol": 48}
            ],
            1: [  # Channel 1 (snare)
                {"row": 8, "note": "D-3", "inst": 1},
                {"row": 24, "note": "D-3", "inst": 1}
            ]
        }
    }
}

Note Format

Field	Type	Description
row	int	Row number (0-based, required)
note	str/int	Note name ("C-4") or MIDI number
inst	int	Instrument index (0-based)
vol	int	Volume (0-64, optional)
effect	int	Effect command hex (optional)
param	int	Effect parameter (optional)

Special Note Values

Value	Meaning
"---" or None	No note
"===" or "OFF"	Note off
"^^^" or "CUT"	Note cut (IT only)
"~~~" or "FADE"	Note fade (IT only)

Named Effects

For readability:

{"row": 0, "note": "C-4", "effect_name": "vibrato", "effect_xy": [3, 4]}

Arrangement

Order of pattern playback:

"arrangement": [
    {"pattern": "intro"},
    {"pattern": "verse", "repeat": 2},
    {"pattern": "chorus"},
    {"pattern": "verse", "repeat": 2},
    {"pattern": "outro"}
],
"restart_position": 1  # Skip intro on loop

Automation

Procedural effects applied during generation:

"automation": [
    {
        "type": "volume_fade",
        "pattern": "intro",
        "channel": 0,
        "start_row": 0,
        "end_row": 32,
        "start_vol": 0,
        "end_vol": 64
    },
    {
        "type": "tempo_change",
        "pattern": "chorus",
        "row": 0,
        "bpm": 140
    }
]

IT-Specific Options

"it_options": {
    "stereo": True,
    "global_volume": 128,
    "mix_volume": 48
}

IT format provides NNA polyphony, pitch envelopes, and filters not available in XM.

Parser Location

All parsers are part of the unified .studio/ infrastructure.

Source: ai_studio_core/templates/project/studio/parsers/

• music.py - Song spec parser (SONG dict → XM/IT file)
• xm_writer.py, xm_types.py - XM format
• it_writer.py, it_types.py - IT format
• sound.py - Instrument synthesis

Setup: Run /init-procgen to install/update the unified .studio/ scaffold.

python .studio/generate.py --only music

File Organization

All specs use .spec.py. The folder determines the type:

.studio/
└── specs/
    ├── instruments/
    │   ├── kick.spec.py       # INSTRUMENT dict
    │   ├── bass.spec.py
    │   └── lead.spec.py
    └── music/
        ├── boss_theme.spec.py  # SONG dict
        └── menu_theme.spec.py

generated/
└── music/
    ├── boss_theme.xm
    └── menu_theme.xm

See Also

• references/song-spec-format.md - Complete format reference
• examples/ - Example song specs
• pattern-design - Pattern layout best practices
• zx-procgen/procedural-instruments - Instrument synthesis