sclass BPMExtractor1 {
  double minBPM = 60, maxBPM = 200;
  
  // 0 if not found
  double getBPM(L<IntRange> ranges) {
    int[] gaps = intRangeStartGaps(ranges);
    if (empty(gaps)) ret 0;
    sort(gaps);
    MultiSet<Int> ms = intArrayAsTreeMultiSet(gaps);
    new Best<Int> best;
    for (int gap : keys(ms))
      if (isBetween_double(
        audio_frequencyImage_pixelsToBPM(gap),
        minBPM, maxBPM))
        best.put(gap, ms.get(gap-1)+ms.get(gap)+ms.get(gap+1));
    Int gap = best!;
    if (gap == null) { print("no fitting gaps"); ret 0; }
    print(ms);
    
    double exactGap = weightedAverage_lit(
      gap-1, ms.get(gap-1),
      gap, ms.get(gap),
      gap+1, ms.get(gap+1));
    double bpm = audio_frequencyImage_pixelsToBPM(exactGap);
    
    printVars_str(+gap, +exactGap, +bpm);
    ret bpm;
  }
}