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;

  }

}