diff --git a/engine/api.py b/engine/api.py
index ef10bc6..0d62f02 100644
--- a/engine/api.py
+++ b/engine/api.py
@@ -10,6 +10,7 @@ from calfbox import cbox
 #Template Modules
 import template.engine.api #we need direct access to the module to inject data in the provided structures. but we also need the functions directly. next line:
 from template.engine.api import *
+from template.engine.duration import baseDurationToTraditionalNumber
 
 #Our modules
 from .pattern import NUMBER_OF_STEPS
@@ -59,7 +60,7 @@ class ClientCallbacks(Callbacks): #inherits from the templates api callbacks
 
     def _timeSignatureChanged(self):
         nr = session.data.howManyUnits
-        typ = session.data.whatTypeOfUnit
+        typ = session.data.whatTypeOfUnit        
         for func in self.timeSignatureChanged:
             func(nr, typ)
 
@@ -73,7 +74,22 @@ class ClientCallbacks(Callbacks): #inherits from the templates api callbacks
         """Subdivisions are tricky, therefore we keep them isolated in their own callback.
         You don't need to redraw anything if you don't want to. One recommendation is to
         draw every n step a little more important (bigger, different color).
-        where n = subdivions"""
+        where n = subdivions
+        
+        We also place JACK BBT via tempoMap here because we need it every time the time sig 
+        changes (which calls _subdivisionsChanged) and if subdivisions change.
+        """
+        typ = baseDurationToTraditionalNumber[session.data.whatTypeOfUnit]        
+        nr = session.data.howManyUnits
+        tradNr = int(nr / session.data.subdivisions)        
+        #JACK BBT for Timebase Master. No matter if we are master at the moment or not.
+        if tradNr == nr / session.data.subdivisions:                        
+            #Easier to read than the else case. Not possible with 9 Steps per Pattern in Groups of 2 because that is a 4.5/4 timesig.
+            session.data.tempoMap.setTimeSignature(tradNr, typ) 
+        else:
+            #Always possible, compared to first if case.             
+            session.data.tempoMap.setTimeSignature(nr, typ*session.data.subdivisions)
+        
         export = session.data.subdivisions
         for func in self.subdivisionsChanged:
             func(export)
@@ -221,30 +237,33 @@ def set_quarterNotesPerMinute(value:int):
         session.data.tempoMap.isTransportMaster = False #triggers rebuild
     elif value == "on":
         assert not session.data.tempoMap.isTransportMaster
-        #keep old bpm value
-        session.data.tempoMap.isTransportMaster = True #triggers rebuild
+        #keep old bpm value. 120 bpm is default.
+        session.data.tempoMap.isTransportMaster = True #triggers rebuild        
     else:
         assert value > 0
         session.data.tempoMap.setQuarterNotesPerMinute(value)
-        session.data.tempoMap.isTransportMaster = True #triggers rebuild
+        session.data.tempoMap.isTransportMaster = True #triggers rebuild        
     #Does not need track rebuilding
     updatePlayback()
-    callbacks._quarterNotesPerMinuteChanged()
-
+    callbacks._quarterNotesPerMinuteChanged()    
+    
 
 def set_whatTypeOfUnit(ticks):
-    if session.data.whatTypeOfUnit == ticks: return
+    """Denominator of Time Signature"""
+    if session.data.whatTypeOfUnit == ticks: return    
     session.data.whatTypeOfUnit = ticks
     session.data.buildAllTracks()
     updatePlayback()
     callbacks._timeSignatureChanged()
 
 def set_howManyUnits(value):
-    if session.data.howManyUnits == value: return
+    """Numerator of Time Signature"""
+    if session.data.howManyUnits == value: return        
     session.data.howManyUnits = value
     session.data.buildAllTracks()
     updatePlayback()
     callbacks._timeSignatureChanged()
+    
 
 def set_subdivisions(value):
     if session.data.subdivisions == value: return