{
  "recordedBeforeOutputsAt": "2026-11-11T21:10:38.391Z",
  "date": "2026-11-12",
  "keyword": "convert mp3 file to midi",
  "firstQuestion": "Should you slow an MP3 before converting it to MIDI, and does mapping the resulting notes back restore the original performance?",
  "sourceMotivation": [
    "T01 explains post-MIDI tempo changes without pitch changes, but does not test slowing source audio before detection.",
    "T02 claims performance timing and velocity survive transcription and offers playback speed controls; a preprocessing-versus-output-edit control is missing.",
    "T03 offers editable tempo/timing and trim-first workflow, but no controlled source-speed/inverse-mapped detector panel."
  ],
  "route": "convert-mp3-file-to-midi-slow-audio",
  "novelty": "New measured source-tempo preprocessing and independently inverse-mapped MIDI, not bitrate history, retained-PCM padding, quiet-note threshold, synthetic PPQ/header changes, meter changes or a repeat of sealed lag diagnosis.",
  "source": "Archived real human GuitarSet1.1.0 microphone performance, not synthesized; same declared consecutive A/B/C/D source excerpts as yesterday, openly reused baseline material, not counted as new originality.",
  "selection": "All first20seconds as consecutive0–5/5–10/10–15/15–20s, unchanged before outputs. No outcome-based window selection.",
  "conditions": [
    {
      "label": "baseline",
      "speed": 1,
      "shift": 0
    },
    {
      "label": "tempo100",
      "speed": 1,
      "shift": 0,
      "filter": "atempo=1.0"
    },
    {
      "label": "tempo075",
      "speed": 0.75,
      "shift": 0,
      "filter": "atempo=0.75"
    },
    {
      "label": "tempo050",
      "speed": 0.5,
      "shift": 0,
      "filter": "atempo=0.5"
    },
    {
      "label": "rate050",
      "speed": 0.5,
      "shift": 12,
      "method": "Same decoded PCM samples written with22050Hz rate; deliberately slows playback and drops nominal pitch one octave, then inverse map adds12 MIDI semitones."
    },
    {
      "label": "tempo125",
      "speed": 1.25,
      "shift": 0,
      "filter": "atempo=1.25"
    }
  ],
  "matching": "Unchanged inherited reference true attacks, exact integer pitch and nearest unused inverse-mapped onset<=150ms, reference time order; carried-in intervals not onset targets. No fitted offset or duration gate. Report unmatched outputs and missed references, not a general accuracy score.",
  "inverseMapping": "Keep raw MIDI untouched. A second saved MIDI changes only tempo500000→500000*speed microseconds/quarter and, for rate050 only, note numbers+12; independently parse and verify mapped seconds=rawSeconds*speed. Output MIDI tempo is an explicit coordinate correction, not detected source BPM.",
  "fixedDetector": "Unchanged production snapshot, Balanced2 throughout. No model or threshold tuning.",
  "groups": [
    "Neutral tempo filter and pitch-preserving slow-source conversions",
    "Half-speed rate change with explicit octave/time correction versus pitch-preserving half-speed",
    "Nonmonotonic preprocessing and reference/event-field tradeoffs including fast1.25 control"
  ],
  "noNewSourceClaims": "No new performance or annotation; new numerical transformations and independent comparisons only."
}