Add example script to modulate parmaters globally

scripts/_plugin_modulation.lua

@@ -0,0 +1,46 @@
+--- session-script example to modulate plugin parameter(s) globally
+--
+-- Ardour > Menu > Session > Scripting > Add Lua Script
+--   "Add" , select "Modulate Plugin Parameter",  click "Add" + OK.
+--
+-----------------------------------------------------------------------------
+-- This script currently assumes you have a track named "Audio"
+-- which as a plugin at the top, where the first parameter has a range > 200
+-- e.g. "No Delay Line"
+-- 
+-- edit below..
+
+
+-- plugin descriptor
+ardour {
+	["type"]    = "session",
+	name        = "Modulate Plugin Parameter",
+	license     = "MIT",
+	author      = "Ardour Lua Task Force",
+	description = [[An example session to modulate a plugin parameter.]]
+}
+
+function factory () -- generate a new script instance
+
+	local count = 0 -- script-instance "global" variable
+
+	-- the "run" function called at the beginning of every process cycle
+	return function (n_samples)
+		count = (count + 1) % 200; -- count process cycles
+		local tri = math.abs (100 - count) -- triangle wave 0..100
+
+		-- get the track named "Audio"
+		-- see also http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:Session
+		-- and http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:Route
+		local route = Session:route_by_name ("Audio")
+		assert (not route:isnil ()) -- make sure it exists
+
+		-- the 1st plugin (from top) on that track, ardour starts counting at zero
+		-- see also http://manual.ardour.org/lua-scripting/class_reference/#ARDOUR:Processor
+		local plugin = route:nth_plugin (0)
+		assert (not plugin:isnil ()) -- make sure it exists
+
+		-- modulate the plugin's first parameter (0)  from  200 .. 300
+		ARDOUR.LuaAPI.set_processor_param (plugin, 0, 200.0 + tri)
+	end
+end