MidiSheetMusic.MidiFile.SplitTrack C# (CSharp) Method

        public static List<MidiTrack> SplitTrack(MidiTrack track, int measurelen)
        {
            List<MidiNote> notes = track.Notes;
            int count = notes.Count;

            MidiTrack top = new MidiTrack(1);
            MidiTrack bottom = new MidiTrack(2);
            List<MidiTrack> result = new List<MidiTrack>(2);
            result.Add(top); result.Add(bottom);

            if (count == 0)
            return result;

            int prevhigh  = 76; /* E5, top of treble staff */
            int prevlow   = 45; /* A3, bottom of bass staff */
            int startindex = 0;

            foreach (MidiNote note in notes) {
            int high, low, highExact, lowExact;

            int number = note.Number;
            high = low = highExact = lowExact = number;

            while (notes[startindex].EndTime < note.StartTime) {
                startindex++;
            }

            /* I've tried several algorithms for splitting a track in two,
             * and the one below seems to work the best:
             * - If this note is more than an octave from the high/low notes
             *   (that start exactly at this start time), choose the closest one.
             * - If this note is more than an octave from the high/low notes
             *   (in this note's time duration), choose the closest one.
             * - If the high and low notes (that start exactly at this starttime)
             *   are more than an octave apart, choose the closest note.
             * - If the high and low notes (that overlap this starttime)
             *   are more than an octave apart, choose the closest note.
             * - Else, look at the previous high/low notes that were more than an
             *   octave apart.  Choose the closeset note.
             */
            FindHighLowNotes(notes, measurelen, startindex, note.StartTime, note.EndTime,
                             ref high, ref low);
            FindExactHighLowNotes(notes, startindex, note.StartTime,
                                  ref highExact, ref lowExact);

            if (highExact - number > 12 || number - lowExact > 12) {
                if (highExact - number <= number - lowExact) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            }
            else if (high - number > 12 || number - low > 12) {
                if (high - number <= number - low) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            }
            else if (highExact - lowExact > 12) {
                if (highExact - number <= number - lowExact) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            }
            else if (high - low > 12) {
                if (high - number <= number - low) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            }
            else {
                if (prevhigh - number <= number - prevlow) {
                    top.AddNote(note);
                }
                else {
                    bottom.AddNote(note);
                }
            }

            /* The prevhigh/prevlow are set to the last high/low
             * that are more than an octave apart.
             */
            if (high - low > 12) {
                prevhigh = high;
                prevlow = low;
            }
            }

            top.Notes.Sort(track.Notes[0]);
            bottom.Notes.Sort(track.Notes[0]);

            return result;
        }