diff --git a/share/scripts/_scl_to_mts.lua b/share/scripts/_scl_to_mts.lua
new file mode 100644
index 0000000000..f4371fcdc3
--- /dev/null
+++ b/share/scripts/_scl_to_mts.lua
@@ -0,0 +1,162 @@
+ardour {
+	["type"]    = "EditorAction",
+	name        = "Scala to MIDI Tuning",
+	license     = "MIT",
+	author      = "Ardour Team",
+	description = [[Read scala (.scl) tuning from a file, generate MIDI tuning standard (MTS) messages and send them to a MIDI port]]
+}
+
+function factory () return function ()
+
+	function portlist ()
+		local rv = {}
+		local a = Session:engine()
+		local _, t = a:get_ports (ARDOUR.DataType("midi"), ARDOUR.PortList())
+		for p in t[2]:iter() do
+			local amp = p:to_asyncmidiport ()
+			if amp:isnil() or not amp:sends_output() then goto continue end
+			rv[amp:name()] = amp
+			--print (amp:name(), amp:sends_output())
+			::continue::
+		end
+		return rv
+	end
+
+	function log2 (v)
+		return math.log (v) / math.log (2)
+	end
+
+	function freq_to_mts (hz)
+		local note = math.floor (12. * log2 (hz / 440) + 69.0)
+		local freq = 440.0 * 2.0 ^ ((note - 69) / 12);
+		assert (freq > note)
+		local cent = 1200.0 * log2 (hz / freq)
+		return note, cent
+	end
+
+	function calc_freq (hz, cent, octave)
+		return hz * 2 ^ ((cent + 1200 * octave) / 1200)
+	end
+
+	local dialog_options = {
+		{ type = "file", key = "file", title = "Select .scl MIDI file" },
+		{ type = "dropdown", key = "port", title = "Target Port", values = portlist () }
+	}
+
+	local rv = LuaDialog.Dialog ("Select Taget", dialog_options):run ()
+	dialog_options = nil -- drop references (ports, shared ptr)
+	collectgarbage () -- and release the references immediately
+
+	if not rv then return end -- user cancelled
+
+	-- read the scl file
+	local freqtbl = {}
+	local ln = 0
+	local expected_len = 0
+	local f = io.open (rv["file"], "r")
+
+	if not f then
+		LuaDialog.Message ("Scala to MTS", "File Not Found", LuaDialog.MessageType.Error, LuaDialog.ButtonType.Close):run ()
+		goto out
+	end
+
+	-- http://www.huygens-fokker.org/scala/scl_format.html
+	freqtbl[1] = 0.0
+	for line in f:lines () do
+		line = string.gsub (line, "%s", "") -- remove all whitespace
+		if line:sub(0,1) == '!' then goto nextline end -- comment
+		ln = ln + 1
+		if ln < 2 then goto nextline end -- name
+		if ln < 3 then
+			expected_len = tonumber (line)
+			goto nextline
+		end
+		local cents
+		if string.find (line, ".", 1, true) then
+			cents = tonumber (line)
+		else
+			local n, d = string.match(line, "(%d+)/(%d+)")
+			if n then
+				cents = 1200 * log2 (n / d)
+			else
+				local n = tonumber (line)
+				cents = 1200 * log2 (n)
+			end
+		end
+		--print ("SCL", ln - 2, cents)
+		freqtbl[ln - 1] = cents
+		::nextline::
+	end
+	f:close ()
+
+	assert (expected_len + 2 == ln)
+	assert (expected_len > 0)
+
+	-- last entry should be an octave
+	assert (freqtbl[expected_len + 1] == 1200)
+
+	-- TODO consider kbm or make these configurable
+	-- http://www.huygens-fokker.org/scala/help.htm#mappings
+	local ref_root = 60 -- middle C
+	local ref_note = 69 -- A4
+	local ref_freq = 440.0
+
+	-- calc frequency at ref_root
+	local ref_base = ref_freq * 2.0 ^ ((ref_root - ref_note) / 12);
+
+	local async_midi_port = rv["port"] -- reference to port
+	local parser = ARDOUR.RawMidiParser () -- construct a MIDI parser
+
+	-- show progress dialog
+	local pdialog = LuaDialog.ProgressWindow ("Scala to MIDI Tuning", true)
+	pdialog:progress (0, "Tuning");
+
+	for nn = 0, 127 do
+		if pdialog:canceled () then break end
+
+		local delta = nn - ref_root
+		local delta_octv = math.floor (delta / expected_len)
+		local delta_note = delta % expected_len
+
+		local fq = calc_freq (ref_base, freqtbl [ delta_note + 1 ], delta_octv)
+		local base, cent = freq_to_mts (fq)
+
+		local cc = math.floor (163.83 * cent + 0.5) | 0
+
+		--print ("MIDI Note:", nn, "scale-note:", delta_note, "Octave:", delta_octv, "-> Freq:", fq, "= note:", base, "+", cent, "cent (", cc, ")")
+
+		local cent_lsb = (cc >> 7) & 127
+		local cent_msb = cc & 127
+
+		local syx = string.char (
+			0xf0, 0x7f, -- realtime sysex
+			0x7f,       -- target-id
+			0x08, 0x02, -- tuning, note change request
+			0x00,       -- tuning program number 0 to 127 in hexadecimal
+			0x01,       -- number of notes to be changed
+			nn,         -- note number to be changed
+			base,       -- semitone (MIDI note number to retune to, unit is 100 cents)
+			cent_msb,   -- MSB of fractional part (1/128 semitone = 100/128 cents = .78125 cent units)
+			cent_lsb,   -- LSB of fractional part (1/16384 semitone = 100/16384 cents = .0061 cent units)
+			0xf7
+		)
+
+		for b = 1, 12 do
+			if parser:process_byte (syx:byte (b)) then
+				async_midi_port:write (parser:midi_buffer (), parser:buffer_size (), 0)
+				-- Physical MIDI is sent at 31.25kBaud.
+				-- Every message is sent as 10bit message on the wire,
+				-- so every MIDI byte needs 320usec.
+				ARDOUR.LuaAPI.usleep (400 * parser:buffer_size ())
+			end
+		end
+
+		pdialog:progress (nn / 127, string.format ("Note %d freq: %.2f (%d + %d)", nn, fq, base, cc))
+		if pdialog:canceled () then break end
+	end
+
+	-- hide modal progress dialog and destroy it
+	pdialog:done ();
+
+	::out::
+end end