[
  {
    "file_id": "host-source",
    "path": "host-source.wav",
    "role": "source_fixture",
    "origin": "author sine 220Hz, not Adobe capture"
  },
  {
    "file_id": "guest-source",
    "path": "guest-source.wav",
    "role": "source_fixture",
    "origin": "author sine 330Hz, not Adobe capture"
  },
  {
    "file_id": "program-mix",
    "path": "program-mix.wav",
    "role": "program_fixture",
    "origin": "author arithmetic sum of two signals, not Adobe export"
  }
]