diff --git a/actions.py b/actions.py
index 1865b03..54f29d2 100644
--- a/actions.py
+++ b/actions.py
@@ -1036,6 +1036,8 @@ class Actions(object):
                 ( r"^reset_selected_modulation$", self.shaders.reset_selected_modulation ),
                 ( r"^reset_modulation_([0-3])$", self.shaders.reset_modulation ),
                 ( r"^select_shader_modulation_slot_([0-3])$", self.shaders.select_shader_modulation_slot ),
+                ( r"^select_next_shader_modulation_slot$", self.shaders.select_next_shader_modulation_slot ),
+                ( r"^select_previous_shader_modulation_slot$", self.shaders.select_previous_shader_modulation_slot ),
                 ( r"^set_shader_speed_layer_offset_([0-2])_amount$",               self.shaders.set_speed_offset_to_amount ),
                 ( r"^set_shader_speed_layer_([0-2])_amount$",                      self.shaders.set_speed_layer_to_amount ),
                 ( r"^set_display_mode_([a-zA-Z_]*)$",  self.set_display_mode )
@@ -1099,9 +1101,8 @@ class Actions(object):
 
         try:
             #print ("for method_name %s, arguments is %s and len is %s, got method %s" % (method_name, arguments, len(signature(method).parameters), method))
-
                 # for the case where cc is being used as switch, we ignore note_off
-            print(type(argument))
+            #print(type(argument))
             if len(signature(method).parameters) == 0 and isinstance(argument, float) and argument == 0:
                 print('cc off ?')
                 return
diff --git a/video_centre/shaders.py b/video_centre/shaders.py
index c0f010a..519cce6 100644
--- a/video_centre/shaders.py
+++ b/video_centre/shaders.py
@@ -6,6 +6,9 @@ from data_centre.plugin_collection import ModulationReceiverPlugin
 class Shaders(object):
     MENU_HEIGHT = 10
     EMPTY_SHADER = dict(name='none',is_shader=True,shad_type='-',param_number=4,path='-')
+
+    MAX_MOD_SLOTS = 4
+
     def __init__(self, root, osc_client, message_handler, data):
         self.root = root
         self.osc_client = osc_client
@@ -25,7 +28,7 @@ class Shaders(object):
 
         self.selected_modulation_slot = 0
         #self.modulation_level = [[[0.0,0.0,0.0,0.0] for i in range(4)] for i in range(3)]
-        self.modulation_value = [0.0,0.0,0.0,0.0]
+        self.modulation_value = [0.0] * self.MAX_MOD_SLOTS #,0.0,0.0,0.0]
 
         #self.load_selected_shader()
 
@@ -177,6 +180,16 @@ class Shaders(object):
     def select_shader_modulation_slot(self, slot):
         self.selected_modulation_slot = slot
 
+    def select_next_shader_modulation_slot(self):
+        self.selected_modulation_slot += 1
+        if self.selected_modulation_slot >= self.MAX_MOD_SLOTS:
+            self.selected_modulation_slot = 0
+
+    def select_previous_shader_modulation_slot(self):
+        self.selected_modulation_slot -= 1
+        if self.selected_modulation_slot < 0:
+            self.selected_modulation_slot = self.MAX_MOD_SLOTS-1
+
     def reset_modulation(self, slot):
         for layer in self.modulation_level:
             for layer,levels in enumerate(layer):