# fm.freemix.stem > Published by [lex-publisher.freemix.fm](https://lexicon.garden/identity/did:plc:bt7c6cqevgefnvej5cmgke4g) ✓ This is the authoritative definition for this NSID. ## Links - [View on Lexicon Garden](https://lexicon.garden/lexicon/did:plc:bt7c6cqevgefnvej5cmgke4g/fm.freemix.stem) - [Documentation](https://lexicon.garden/lexicon/did:plc:bt7c6cqevgefnvej5cmgke4g/fm.freemix.stem/docs) - [Examples](https://lexicon.garden/lexicon/did:plc:bt7c6cqevgefnvej5cmgke4g/fm.freemix.stem/examples) ## Definitions ### `fm.freemix.stem` **Type**: `record` A stem (isolated track component). Top-level leaf (FM-549 s38: pulled out from under release.* ; release.stem -> stem). May optionally reference a parent track and/or a parent stems-group. **Key**: `tid` | Property | Type | Required | Description | |----------|------|----------|-------------| | `tags` | `array` | No | Freeform tags | | `label` | `string` | Yes | Human-readable name (e.g., 'Main Vocal', 'Acid Line', '808 Kit') | | `notes` | `string` | No | Generic freeform notes for this stem (FM-550, s41). Any purpose — processing notes, licensing caveats, or an ad-hoc credit like 'Drummer: Joey Beats'. Deliberately NOT the structured #trackCredits block: most credit roles are meaningless on a stem, so a freeform escape hatch covers the rare case. Stems carry no structured credits. | | `title` | `string` | No | Stem title (first-class stems). `label` remains the required human-readable name; `title` is the unified-on-title field added in FM-504 | | `genres` | `array` | No | Genre classifications. Deliberately plural `genres` (it IS an array), NOT the track lexicon's singular `genre` — singular-for-an-array is misleading. Intentional divergence. | | `license` | `string` (at-uri) | No | AT URI of the license grant record. For child stems this is the parent track's license, copied down at creation (FM-504) | | `audioUrl` | `string` (uri) | No | DEPRECATED (FM-508): no longer emitted. Stem audio is private (gated download / app-served preview) and is never surfaced in the portable record. Field kept (optional) to tolerate pre-FM-508 records without a putRecord rewrite. Stems never get a public clip. | | `position` | `integer` | No | Display order position (0-indexed) | | `stemType` | `string` | Yes | Type/category of the stem | | `audioHash` | `string` | Yes | SHA-256 hash of the stem audio content | | `bpmCentis` | `integer` | No | Centi-BPM (BPM × 100), integer — the Lexicon model has no float type; decode as `bpmCentis / 100` on read. Mirrors `fm.freemix.release.track`. | | `createdAt` | `string` (datetime) | Yes | Record creation timestamp | | `detachedAt` | `string` (datetime) | No | FM-504 tombstone: when the parent link was severed | | `musicalKey` | `string` | No | Musical key (e.g., 'Am', 'F#m', 'Bb'). Deliberately named `musicalKey`, NOT the track lexicon's `key`: `key` is dangerously overloaded in a data layer (record keys, rkeys, map keys), so `musicalKey` is collision-proof and self-documenting. Intentional divergence. | | `audioFormat` | `string` | Yes | Audio file format | | `coverArtUrl` | `string` (uri) | No | URL to cover art image | | `description` | `string` | No | Stem description | | `parentGroup` | `string` (at-uri) | No | AT URI of the parent fm.freemix.group.stems this stem belongs to (optional). FM-549 s38: stems may carry an optional parentTrack AND an optional parentGroup back-ref — the only upward refs in the model (containers otherwise point down at members). | | `parentTrack` | `string` (at-uri) | No | AT URI of the parent track this stem belongs to (optional for standalone stems) | | `aiDeclaration` | `object` | No | Declaration of AI involvement in creation | | `audioSizeBytes` | `integer` | Yes | Size of the audio file in bytes | | `parentGroupCid` | `string` (cid) | No | CID of the parent stems-group record (pins to exact version). | | `parentTrackCid` | `string` (cid) | No | CID of the parent track record (pins to exact version) | | `audioDurationMs` | `integer` | Yes | Duration of the stem in milliseconds | | `previouslyAttachedToCid` | `string` (cid) | No | FM-504 tombstone: CID of the former parent track record at detach time | | `previouslyAttachedToUri` | `string` (at-uri) | No | FM-504 tombstone: AT URI of the former parent track, set when this stem was detached (parent deleted, keep-stems path). Preserves remix-tree placement + royalty-lineage reconstructability | ## Raw Schema ```json { "id": "fm.freemix.stem", "defs": { "main": { "key": "tid", "type": "record", "record": { "type": "object", "required": [ "stemType", "label", "audioHash", "audioDurationMs", "audioFormat", "audioSizeBytes", "createdAt" ], "properties": { "tags": { "type": "array", "items": { "type": "string", "maxLength": 50 }, "maxLength": 10, "description": "Freeform tags" }, "label": { "type": "string", "maxLength": 100, "description": "Human-readable name (e.g., 'Main Vocal', 'Acid Line', '808 Kit')" }, "notes": { "type": "string", "maxLength": 1000, "description": "Generic freeform notes for this stem (FM-550, s41). Any purpose — processing notes, licensing caveats, or an ad-hoc credit like 'Drummer: Joey Beats'. Deliberately NOT the structured #trackCredits block: most credit roles are meaningless on a stem, so a freeform escape hatch covers the rare case. Stems carry no structured credits." }, "title": { "type": "string", "maxLength": 300, "description": "Stem title (first-class stems). `label` remains the required human-readable name; `title` is the unified-on-title field added in FM-504" }, "genres": { "type": "array", "items": { "type": "string", "maxLength": 50 }, "maxLength": 10, "description": "Genre classifications. Deliberately plural `genres` (it IS an array), NOT the track lexicon's singular `genre` — singular-for-an-array is misleading. Intentional divergence." }, "license": { "type": "string", "format": "at-uri", "maxLength": 3000, "description": "AT URI of the license grant record. For child stems this is the parent track's license, copied down at creation (FM-504)" }, "audioUrl": { "type": "string", "format": "uri", "maxLength": 3000, "description": "DEPRECATED (FM-508): no longer emitted. Stem audio is private (gated download / app-served preview) and is never surfaced in the portable record. Field kept (optional) to tolerate pre-FM-508 records without a putRecord rewrite. Stems never get a public clip." }, "position": { "type": "integer", "minimum": 0, "description": "Display order position (0-indexed)" }, "stemType": { "type": "string", "maxLength": 100, "description": "Type/category of the stem", "knownValues": [ "drums", "bass", "vocals", "synth", "guitar", "keys", "pad", "lead", "fx", "other" ] }, "audioHash": { "type": "string", "maxLength": 200, "description": "SHA-256 hash of the stem audio content" }, "bpmCentis": { "type": "integer", "maximum": 99900, "minimum": 2000, "description": "Centi-BPM (BPM × 100), integer — the Lexicon model has no float type; decode as `bpmCentis / 100` on read. Mirrors `fm.freemix.release.track`." }, "createdAt": { "type": "string", "format": "datetime", "maxLength": 100, "description": "Record creation timestamp" }, "detachedAt": { "type": "string", "format": "datetime", "maxLength": 100, "description": "FM-504 tombstone: when the parent link was severed" }, "musicalKey": { "type": "string", "maxLength": 10, "description": "Musical key (e.g., 'Am', 'F#m', 'Bb'). Deliberately named `musicalKey`, NOT the track lexicon's `key`: `key` is dangerously overloaded in a data layer (record keys, rkeys, map keys), so `musicalKey` is collision-proof and self-documenting. Intentional divergence." }, "audioFormat": { "type": "string", "maxLength": 100, "description": "Audio file format", "knownValues": [ "wav", "flac", "mp3" ] }, "coverArtUrl": { "type": "string", "format": "uri", "maxLength": 3000, "description": "URL to cover art image" }, "description": { "type": "string", "maxLength": 5000, "description": "Stem description" }, "parentGroup": { "type": "string", "format": "at-uri", "maxLength": 3000, "description": "AT URI of the parent fm.freemix.group.stems this stem belongs to (optional). FM-549 s38: stems may carry an optional parentTrack AND an optional parentGroup back-ref — the only upward refs in the model (containers otherwise point down at members)." }, "parentTrack": { "type": "string", "format": "at-uri", "maxLength": 3000, "description": "AT URI of the parent track this stem belongs to (optional for standalone stems)" }, "aiDeclaration": { "type": "object", "required": [ "category" ], "properties": { "tools": { "type": "array", "items": { "type": "string", "maxLength": 100 }, "maxLength": 10, "description": "AI tools used" }, "category": { "type": "string", "maxLength": 100, "description": "Level of AI involvement", "knownValues": [ "none", "assisted", "augmented", "generated" ] }, "description": { "type": "string", "maxLength": 1000, "description": "Creator's description of how AI was used" } }, "description": "Declaration of AI involvement in creation" }, "audioSizeBytes": { "type": "integer", "description": "Size of the audio file in bytes" }, "parentGroupCid": { "type": "string", "format": "cid", "maxLength": 200, "description": "CID of the parent stems-group record (pins to exact version)." }, "parentTrackCid": { "type": "string", "format": "cid", "maxLength": 200, "description": "CID of the parent track record (pins to exact version)" }, "audioDurationMs": { "type": "integer", "description": "Duration of the stem in milliseconds" }, "previouslyAttachedToCid": { "type": "string", "format": "cid", "maxLength": 200, "description": "FM-504 tombstone: CID of the former parent track record at detach time" }, "previouslyAttachedToUri": { "type": "string", "format": "at-uri", "maxLength": 3000, "description": "FM-504 tombstone: AT URI of the former parent track, set when this stem was detached (parent deleted, keep-stems path). Preserves remix-tree placement + royalty-lineage reconstructability" } } }, "description": "A stem (isolated track component). Top-level leaf (FM-549 s38: pulled out from under release.* ; release.stem -> stem). May optionally reference a parent track and/or a parent stems-group." } }, "$type": "com.atproto.lexicon.schema", "lexicon": 1 } ```