diff --git a/engine/track.py b/engine/track.py
index ee7be09..b828910 100644
--- a/engine/track.py
+++ b/engine/track.py
@@ -490,7 +490,7 @@ class Track(object):
         copy = block.copy(newParentTrack=self, nameSuffix="-reserved")
 
         copy.data = list() #empty
-        copy.minimumInTicks = self.duration()
+        copy.minimumInTicks = block.duration()
 
         self.blocks.insert(index +1, copy)
         self.toPosition(originalPosition) #has head() in it
@@ -1306,14 +1306,29 @@ class Track(object):
                         currentSubGroupFlag = obj["flag"]
                         subBeamGroups[-1].append(obj)
 
+
+                previous_subGroup_firstNoteDuration = 0
+                previous_subGroup_lastNoteDuration = 0
+
                 for subBeamGroup in subBeamGroups:
                     for obj in subBeamGroup:
                         startStaffLine = obj[startDotOnLineKeyword]
-                        length = beamPosition - startStaffLine
+                        length = beamPosition - startStaffLine #vertical, in stafflines.
                         obj["beam"]  = (startStaffLine, length, direction) #(starting point, length, 1|-)] 1 stem is on the right or -1 left side of the note.
                     firstItem, lastItem = subBeamGroup[0], subBeamGroup[-1]
-                    connectorLength = lastItem["completeDuration"] if not lastItem == beamGroup[-1] else 0
+
+                    #Now calculate the horizontal length.
+                    #This is difficult because you can mix durations e.g. 16th and 8th in the same beam.
+                    #This syncopation 16 8 16  has the 8th in the middle. If any of the 16th beams connects to the left or right side this would be indistinguishable from a 16th note.
+                    #It is also difficult because it is on the boundary of subBeamGroups
+
+                    if not lastItem == beamGroup[-1]:
+                        connectorLength = lastItem["completeDuration"]
+                    elif lastItem == beamGroup[-1]:
+                        connectorLength = 0
+
                     resultBeamGroups.append((firstItem["tickindex"], lastItem["tickindex"] + connectorLength, abs(firstItem["flag"]), beamPosition, direction)) #tick-start, tick-end, duration-type, position as staffline. Extra simple for the GUI.
+
         #Beams finished
 
         resultAppend(metaData)