{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "title": "InstrumentTablatureScore",
  "description": "Schema for validating musical instrument tablature structures, supporting multi-voice polyphony, chords, rests, and ties.",
  "type": "object",
  "required": ["id", "title", "instrument", "timeSignature", "measures"],
  "properties": {
    "id": {
      "type": "string",
      "description": "Unique identifier for the musical score."
    },
    "title": {
      "type": "string",
      "description": "The title of the piece or exercise."
    },
    "instrument": {
      "type": "string",
      "description": "The target musical instrument for this tablature (e.g., 'Guitalele')."
    },
    "description": {
      "type": "string",
      "description": "An optional summary or stylistic context regarding the arrangement."
    },
    "timeSignature": {
      "type": "string",
      "pattern": "^\\d+/\\d+$",
      "description": "The time signature of the piece formatted as 'Beats/BeatUnit' (e.g., '4/4', '2/4', '6/8')."
    },
    "measures": {
      "type": "array",
      "description": "The chronologically ordered list of bars or measures making up the score.",
      "items": {
        "type": "object",
        "required": ["measureNumber", "notes"],
        "properties": {
          "measureNumber": {
            "type": "integer",
            "minimum": 1,
            "description": "The sequential number of the measure within the score."
          },
          "notes": {
            "type": "array",
            "description": "A collection of sequential or overlapping musical events (notes, rests, chords) within this measure.",
            "items": {
              "type": "object",
              "required": ["duration"],
              "properties": {
                "duration": {
                  "type": "number",
                  "minimum": 0,
                  "description": "The rhythmic duration of the musical event in beats (e.g., 4.0 for a whole note, 1.0 for a quarter note, 0.5 for an eighth note in common time)."
                },
                "fret": {
                  "type": ["integer", "null"],
                  "minimum": 0,
                  "description": "The fret position to press. An integer value means a specific fret, 0 means open string, and null implies a uniquely muted/dead fret scenario or dynamic placement instruction."
                },
                "string": {
                  "type": "integer",
                  "minimum": 1,
                  "description": "The physical string line index on the instrument fretboard."
                },
                "voice": {
                  "type": "integer",
                  "minimum": 1,
                  "description": "Used in polyphonic lines to differentiate parallel voice tracks within the same time space (e.g., Voice 1 for melody, Voice 2 for bass line)."
                },
                "tie": {
                  "type": "boolean",
                  "description": "Indicates that the sound of this note sustains seamlessly into the immediate following note configuration."
                },
                "description": {
                  "type": "string",
                  "description": "Optional educational text or playback annotations tied to this particular note action."
                },
                "pitches": {
                  "type": "array",
                  "description": "Defines a simultaneous chord profile. When present, individual string/fret combinations move here instead of the root object mapping.",
                  "items": {
                    "type": "object",
                    "required": ["string"],
                    "properties": {
                      "fret": {
                        "type": ["integer", "null"],
                        "minimum": 0,
                        "description": "The specific fret position for this piece of the chord array block."
                      },
                      "string": {
                        "type": "integer",
                        "minimum": 1,
                        "description": "The target string designation for this coordinate block entry."
                      }
                    }
                  }
                }
              },
              "allOf": [
                {
                  "comment": "If string is present, fret must be declared too (even if null). Validates standard single notes.",
                  "if": { "required": ["string"] },
                  "then": { "required": ["fret"] }
                },
                {
                  "comment": "If neither pitches nor string/fret are populated, this object represents a musical rest.",
                  "if": {
                    "not": { "required": ["string"] }
                  },
                  "then": {
                    "not": { "required": ["pitches"] }
                  }
                }
              ]
            }
          }
        }
      }
    }
  }
}