diff --git a/share/scripts/_ab_switch.lua b/share/scripts/ab_switch.lua
similarity index 80%
rename from share/scripts/_ab_switch.lua
rename to share/scripts/ab_switch.lua
index e531178df1..fc238b8669 100644
--- a/share/scripts/_ab_switch.lua
+++ b/share/scripts/ab_switch.lua
@@ -4,14 +4,17 @@ ardour {
 	category    = "Amplifier",
 	license     = "MIT",
 	author      = "Ardour Team",
-	description = [[Auotomatable A/B Input Select. Channels are mapped in pairs: In 1/2 -> Out 1, In 3/4 -> Out 2, etc.]]
+	description = [[Auotomatable A/B Input Select. Channels grouped:
+Mono out:  In 1/2 -> Out 1
+Stereo out: In 1/3 -> Out 1, In 2/4 -> Out 2
+Quad out: In 1/5 -> Out 1, In 2/6 -> Out 2, In 3/7 -> Out 3, In 4/8 -> Out 4
+]]
 }
 
 function dsp_ioconfig ()
 	return {
+		connect_all_audio_outputs = true, -- override strict-i/o
 		-- in theory any combination with N_in = 2 * N_out is possible
-		-- (and we should inform the host to override strict-i/o
-		-- connect_all_audio_outputs = true)
 		{ audio_in = 2, audio_out = 1},
 		{ audio_in = 4, audio_out = 2},
 		{ audio_in = 8, audio_out = 4},
@@ -51,28 +54,29 @@ function dsp_runmap (bufs, in_map, out_map, n_samples, offset)
 			goto next
 		end
 
-		local in_a = c * 2 - 1
-		local in_b = c * 2
+		local in_a = c
+		local in_b = c + n_aout
 		local ia = in_map:get (ARDOUR.DataType ("audio"), in_a - 1)
 		local ib = in_map:get (ARDOUR.DataType ("audio"), in_b - 1)
 
 		local buf_aout = bufs:get_audio(o)
 
-		-- optimize fixed gain case
+		-- optimize fixed gain case (copy buffers)
 		if cur_a == target_A and cur_b == target_B then
 			if target_A == 1.0 then
-				-- the first (and only first) channel may be in-place
+				-- the first set of channels channel may be in-place
 				if buf_aout ~= bufs:get_audio(ia) then
 					buf_aout:read_from (bufs:get_audio(ia):data (0), n_samples, offset, offset)
 				end
 			else
 				assert (buf_aout ~= bufs:get_audio(ib))
+				assert (target_B == 1.0)
 				buf_aout:read_from (bufs:get_audio(ib):data (0), n_samples, offset, offset)
 			end
 			goto next
 		end
 
-		-- apply gain to each input channel
+		-- apply gain to each input channel in-place
 		if ia ~= ARDOUR.ChanMapping.Invalid and ia ~= ib then
 			cur_a = ARDOUR.Amp.apply_gain (bufs:get_audio(ia), sr, n_samples, gA, target_A, offset)
 		end
@@ -83,7 +87,7 @@ function dsp_runmap (bufs, in_map, out_map, n_samples, offset)
 		-- channels are supposed to be in linear order
 		assert (buf_aout ~= bufs:get_audio(ib))
 
-		-- copy input to output if needed (first channel may be in-place)
+		-- copy input to output if needed (first set of channels may be in-place)
 		if buf_aout ~= bufs:get_audio(ia) then
 			buf_aout:read_from (bufs:get_audio(ia):data (0), n_samples, offset, offset)
 		end
diff --git a/share/scripts/x-fade.lua b/share/scripts/x-fade.lua
new file mode 100644
index 0000000000..804ac5396b
--- /dev/null
+++ b/share/scripts/x-fade.lua
@@ -0,0 +1,102 @@
+ardour {
+	["type"]    = "dsp",
+	name        = "a-Cross Fade",
+	category    = "Amplifier",
+	license     = "MIT",
+	author      = "Ardour Team",
+	description = [[Auotomatable Crossfade. Channels are grouped:
+Mono out:  In 1/2 -> Out 1
+Stereo out: In 1/3 -> Out 1, In 2/4 -> Out 2
+Quad out: In 1/5 -> Out 1, In 2/6 -> Out 2, In 3/7 -> Out 3, In 4/8 -> Out 4
+]]
+}
+
+function dsp_ioconfig ()
+	return {
+		connect_all_audio_outputs = true, -- override strict-i/o
+		-- in theory any combination with N_in = 2 * N_out is possible
+		{ audio_in = 2, audio_out = 1},
+		{ audio_in = 4, audio_out = 2},
+		{ audio_in = 8, audio_out = 4},
+	}
+end
+
+function dsp_params ()
+	return { { ["type"] = "input", name = "A/B", min = 0, max = 1, default = 0} }
+end
+
+local sr = 48000
+local cur_a = 0.0
+local cur_b = 0.0
+
+local n_aout = 0
+
+function dsp_init (rate)
+	sr = rate
+end
+
+function dsp_configure (ins, outs)
+	n_ainp = ins:n_audio ()
+	n_aout = outs:n_audio ()
+	assert (n_aout * 2 == n_ainp)
+end
+
+-- the DSP callback function
+function dsp_runmap (bufs, in_map, out_map, n_samples, offset)
+	local ctrl = CtrlPorts:array() -- get control port array
+	local target_B = ctrl[1]
+	local target_A = 1 - target_B
+
+	local gA = cur_a
+	local gB = cur_b
+
+	for c = 1, n_aout do
+		local o = out_map:get (ARDOUR.DataType ("audio"), c - 1)
+		if o == ARDOUR.ChanMapping.Invalid then
+			goto next
+		end
+
+		local in_a = c
+		local in_b = c + n_aout
+		local ia = in_map:get (ARDOUR.DataType ("audio"), in_a - 1)
+		local ib = in_map:get (ARDOUR.DataType ("audio"), in_b - 1)
+
+		local buf_aout = bufs:get_audio(o)
+
+		-- optimize hard A/B fixed gain case (copy buffers)
+		if cur_a == target_A and cur_b == target_B then
+			if target_A == 1.0 then
+				-- the first (and only first) channel may be in-place
+				if buf_aout ~= bufs:get_audio(ia) then
+					buf_aout:read_from (bufs:get_audio(ia):data (0), n_samples, offset, offset)
+				end
+				goto next
+			elseif target_B == 1.0 then
+				assert (buf_aout ~= bufs:get_audio(ib))
+				buf_aout:read_from (bufs:get_audio(ib):data (0), n_samples, offset, offset)
+				goto next
+			end
+		end
+
+		-- apply gain to each input channel in-place
+		if ia ~= ARDOUR.ChanMapping.Invalid and ia ~= ib then
+			cur_a = ARDOUR.Amp.apply_gain (bufs:get_audio(ia), sr, n_samples, gA, target_A, offset)
+		end
+		if ib ~= ARDOUR.ChanMapping.Invalid and ia ~= ib then
+			cur_b = ARDOUR.Amp.apply_gain (bufs:get_audio(ib), sr, n_samples, gB, target_B, offset)
+		end
+
+		-- channels are supposed to be in linear order
+		assert (buf_aout ~= bufs:get_audio(ib))
+
+		-- copy input to output if needed (first set of channels may be in-place)
+		if buf_aout ~= bufs:get_audio(ia) then
+			buf_aout:read_from (bufs:get_audio(ia):data (0), n_samples, offset, offset)
+		end
+
+		-- add the second buffer
+		ARDOUR.DSP.mix_buffers_no_gain (buf_aout:data (offset), bufs:get_audio(ib):data (offset), n_samples)
+
+		::next::
+	end
+end