diff --git a/tracker/action.go b/tracker/action.go
index 6faf6a7..f4b857c 100644
--- a/tracker/action.go
+++ b/tracker/action.go
@@ -93,6 +93,16 @@ type (
 		*Model
 	}
 	ShowLicense Model
+
+	ChooseSendSource struct {
+		ID int
+		*Model
+	}
+	ChooseSendTarget struct {
+		ID   int
+		Port int
+		*Model
+	}
 )
 
 // Action methods
@@ -517,6 +527,40 @@ func (d DeleteOrderRow) Do() {
 	m.d.Cursor2.OrderRow = m.d.Cursor.OrderRow
 }
 
+// ChooseSendSource
+
+func (m *Model) IsChoosingSendTarget() bool {
+	return m.d.SendSource > 0
+}
+
+func (m *Model) ChooseSendSource(id int) Action {
+	return MakeEnabledAction(ChooseSendSource{ID: id, Model: m})
+}
+func (s ChooseSendSource) Do() {
+	defer (*Model)(s.Model).change("ChooseSendSource", NoChange, MinorChange)()
+	s.Model.d.SendSource = s.ID
+}
+
+// ChooseSendTarget
+
+func (m *Model) ChooseSendTarget(id int, port int) Action {
+	return MakeEnabledAction(ChooseSendTarget{ID: id, Port: port, Model: m})
+}
+func (s ChooseSendTarget) Do() {
+	defer (*Model)(s.Model).change("ChooseSendTarget", SongChange, MinorChange)()
+	sourceID := (*Model)(s.Model).d.SendSource
+	s.d.SendSource = 0
+	if sourceID <= 0 || s.ID <= 0 || s.Port < 0 || s.Port > 7 {
+		return
+	}
+	si, su, err := s.d.Song.Patch.FindUnit(sourceID)
+	if err != nil {
+		return
+	}
+	s.d.Song.Patch[si].Units[su].Parameters["target"] = s.ID
+	s.d.Song.Patch[si].Units[su].Parameters["port"] = s.Port
+}
+
 // NewSong
 
 func (m *Model) NewSong() Action { return MakeEnabledAction((*NewSong)(m)) }
diff --git a/tracker/derived.go b/tracker/derived.go
index cd20f47..16cf92a 100644
--- a/tracker/derived.go
+++ b/tracker/derived.go
@@ -176,6 +176,7 @@ func (m *Model) deriveParams(unit *sointu.Unit) []Parameter {
 	if !ok {
 		return ret
 	}
+	portIndex := 0
 	for i, up := range unitType {
 		if !up.CanSet && !up.CanModulate {
 			continue // skip parameters that cannot be set or modulated
@@ -186,7 +187,12 @@ func (m *Model) deriveParams(unit *sointu.Unit) []Parameter {
 		if unit.Type == "send" && up.Name == "port" {
 			continue
 		}
-		ret = append(ret, Parameter{m: m, unit: unit, up: &unitType[i], vtable: &namedParameter{}})
+		q := 0
+		if up.CanModulate {
+			portIndex++
+			q = portIndex
+		}
+		ret = append(ret, Parameter{m: m, unit: unit, up: &unitType[i], vtable: &namedParameter{}, port: q})
 	}
 	if unit.Type == "oscillator" && unit.Parameters["type"] == sointu.Sample {
 		ret = append(ret, Parameter{m: m, unit: unit, vtable: &gmDlsEntryParameter{}})
diff --git a/tracker/gioui/knob.go b/tracker/gioui/knob.go
index 8710711..16e7404 100644
--- a/tracker/gioui/knob.go
+++ b/tracker/gioui/knob.go
@@ -149,15 +149,6 @@ func (k *KnobWidget) update(gtx C) {
 	}
 }
 
-func (k *KnobWidget) strokeBg(gtx C) {
-	diam := gtx.Dp(k.Style.Diameter)
-	circle := clip.Ellipse{
-		Min: image.Pt(0, 0),
-		Max: image.Pt(diam, diam),
-	}.Op(gtx.Ops)
-	paint.FillShape(gtx.Ops, k.Style.Bg, circle)
-}
-
 func (k *KnobWidget) strokeKnobArc(gtx C, color color.NRGBA, strokeWidth, diameter int, start, end float32) {
 	rad := float32(diameter) / 2
 	end = min(max(end, 0), 1)
diff --git a/tracker/gioui/port.go b/tracker/gioui/port.go
new file mode 100644
index 0000000..36b3b1b
--- /dev/null
+++ b/tracker/gioui/port.go
@@ -0,0 +1,66 @@
+package gioui
+
+import (
+	"image"
+	"image/color"
+	"math"
+
+	"gioui.org/f32"
+	"gioui.org/gesture"
+	"gioui.org/io/event"
+	"gioui.org/op/clip"
+	"gioui.org/op/paint"
+	"gioui.org/unit"
+)
+
+type (
+	PortState struct {
+		click gesture.Click
+	}
+
+	PortStyle struct {
+		Diameter    unit.Dp
+		StrokeWidth unit.Dp
+		Color       color.NRGBA
+	}
+
+	PortWidget struct {
+		Theme *Theme
+		Style *PortStyle
+		State *PortState
+	}
+)
+
+func Port(t *Theme, p *PortState) PortWidget {
+	return PortWidget{Theme: t, Style: &t.Port, State: p}
+}
+
+func (p *PortWidget) Layout(gtx C) D {
+	d := gtx.Dp(p.Style.Diameter)
+	defer clip.Rect(image.Rectangle{Max: image.Pt(d, d)}).Push(gtx.Ops).Pop()
+	event.Op(gtx.Ops, p.State)
+	p.State.click.Add(gtx.Ops)
+	p.strokeCircle(gtx)
+	return D{Size: image.Pt(d, d)}
+}
+
+func (p *PortState) Clicked(gtx C) bool {
+	ev, ok := p.click.Update(gtx.Source)
+	return ok && ev.Kind == gesture.KindClick
+}
+
+func (p *PortWidget) strokeCircle(gtx C) {
+	sw := float32(gtx.Dp(p.Style.StrokeWidth))
+	d := float32(gtx.Dp(p.Style.Diameter))
+	rad := d / 2
+	center := f32.Point{X: rad, Y: rad}
+	var path clip.Path
+	path.Begin(gtx.Ops)
+	path.MoveTo(f32.Pt(sw/2, rad))
+	path.ArcTo(center, center, float32(math.Pi*2))
+	paint.FillShape(gtx.Ops, p.Style.Color,
+		clip.Stroke{
+			Path:  path.End(),
+			Width: sw,
+		}.Op())
+}
diff --git a/tracker/gioui/theme.go b/tracker/gioui/theme.go
index f52552e..1d9f70e 100644
--- a/tracker/gioui/theme.go
+++ b/tracker/gioui/theme.go
@@ -85,16 +85,20 @@ type Theme struct {
 		}
 	}
 	UnitEditor struct {
-		Name          LabelStyle
-		Chooser       LabelStyle
-		Hint          LabelStyle
-		InvalidParam  color.NRGBA
-		SendTarget    color.NRGBA
-		Width         unit.Dp
-		Height        unit.Dp
-		RowTitle      LabelStyle
-		RowTitleWidth unit.Dp
-		Error         color.NRGBA
+		Name         LabelStyle
+		Chooser      LabelStyle
+		Hint         LabelStyle
+		InvalidParam color.NRGBA
+		SendTarget   color.NRGBA
+		Width        unit.Dp
+		Height       unit.Dp
+		UnitList     struct {
+			LabelWidth unit.Dp
+			Name       LabelStyle
+			Disabled   LabelStyle
+			Error      color.NRGBA
+		}
+		Error color.NRGBA
 	}
 	Cursor    CursorStyle
 	Selection CursorStyle
@@ -110,6 +114,7 @@ type Theme struct {
 	ScrollBar  ScrollBarStyle
 	Knob       KnobStyle
 	SignalRail SignalRailStyle
+	Port       PortStyle
 
 	// iconCache is used to cache the icons created from iconvg data
 	iconCache map[*byte]*widget.Icon
diff --git a/tracker/gioui/theme.yml b/tracker/gioui/theme.yml
index 8574c0d..ad2659e 100644
--- a/tracker/gioui/theme.yml
+++ b/tracker/gioui/theme.yml
@@ -214,9 +214,12 @@ uniteditor:
   sendtarget: *secondarycolor
   width: 60
   height: 70
-  rowtitle: { textsize: 12, color: *white, alignment: 2 }
-  rowtitlewidth: 16
-  error: *errorcolor
+  unitlist:
+    labelwidth: 16
+    name: { textsize: 12, color: *white, alignment: 2 }
+    disabled:
+      { textsize: 12, color: *disabled, font: { style: 1 }, alignment: 2 }
+    error: *errorcolor
 knob:
   diameter: 36
   value: { textsize: 12, color: *highemphasis }
@@ -231,3 +234,7 @@ signalrail:
   linewidth: 2
   portdiameter: 8
   portcolor: *primarycolor
+port:
+  diameter: 36
+  strokewidth: 4
+  color: *secondarycolor
diff --git a/tracker/gioui/unit_editor.go b/tracker/gioui/unit_editor.go
index 381c96e..d055fb8 100644
--- a/tracker/gioui/unit_editor.go
+++ b/tracker/gioui/unit_editor.go
@@ -31,7 +31,7 @@ type (
 	UnitEditor struct {
 		paramTable     *ScrollTable
 		searchList     *DragList
-		Parameters     [][]*ParameterWidget
+		Parameters     [][]*ParameterState
 		DeleteUnitBtn  *Clickable
 		CopyUnitBtn    *Clickable
 		ClearUnitBtn   *Clickable
@@ -157,18 +157,18 @@ func (pe *UnitEditor) layoutRack(gtx C) D {
 	// create enough parameter widget to match the number of parameters
 	width := pe.paramTable.Table.Width()
 	for len(pe.Parameters) < pe.paramTable.Table.Height() {
-		pe.Parameters = append(pe.Parameters, make([]*ParameterWidget, 0))
+		pe.Parameters = append(pe.Parameters, make([]*ParameterState, 0))
 	}
 	cellWidth := gtx.Dp(t.Theme.UnitEditor.Width)
 	cellHeight := gtx.Dp(t.Theme.UnitEditor.Height)
-	rowTitleLabelWidth := gtx.Dp(t.Theme.UnitEditor.RowTitleWidth)
+	rowTitleLabelWidth := gtx.Dp(t.Theme.UnitEditor.UnitList.LabelWidth)
 	rowTitleSignalWidth := gtx.Dp(t.Theme.SignalRail.SignalWidth) * t.SignalRail().MaxWidth()
 	rowTitleWidth := rowTitleLabelWidth + rowTitleSignalWidth
 	signalError := t.SignalRail().Error()
 	columnTitleHeight := gtx.Dp(0)
 	for i := range pe.Parameters {
 		for len(pe.Parameters[i]) < width {
-			pe.Parameters[i] = append(pe.Parameters[i], &ParameterWidget{})
+			pe.Parameters[i] = append(pe.Parameters[i], &ParameterState{})
 		}
 	}
 	coltitle := func(gtx C, x int) D {
@@ -184,9 +184,12 @@ func (pe *UnitEditor) layoutRack(gtx C) D {
 		}
 
 		sr := SignalRail(t.Theme, t.SignalRail().Item(y))
-		label := Label(t.Theme, &t.Theme.UnitEditor.RowTitle, t.Units().Item(y).Type)
-		if signalError.Err != nil && signalError.UnitIndex == y {
-			label.Color = t.Theme.UnitEditor.Error
+		label := Label(t.Theme, &t.Theme.UnitEditor.UnitList.Name, t.Units().Item(y).Type)
+		switch {
+		case t.Units().Item(y).Disabled:
+			label.LabelStyle = t.Theme.UnitEditor.UnitList.Disabled
+		case signalError.Err != nil && signalError.UnitIndex == y:
+			label.Color = t.Theme.UnitEditor.UnitList.Error
 		}
 		gtx.Constraints = layout.Exact(image.Pt(rowTitleWidth, cellHeight))
 		sr.Layout(gtx)
@@ -210,10 +213,8 @@ func (pe *UnitEditor) layoutRack(gtx C) D {
 			paint.FillShape(gtx.Ops, c, clip.Rect{Min: image.Pt(0, 0), Max: image.Pt(gtx.Constraints.Min.X, gtx.Constraints.Min.Y)}.Op())
 		}
 
-		param := t.Model.Params().Item(tracker.Point{X: x, Y: y})
-		pe.Parameters[y][x].Parameter = param
-		paramStyle := t.ParamStyle(t.Theme, pe.Parameters[y][x])
-		paramStyle.Focus = pe.paramTable.Table.Cursor() == tracker.Point{X: x, Y: y}
+		param := t.Model.Params().Item(point)
+		paramStyle := t.ParamStyle(param, t.Theme, pe.Parameters[y][x], pe.paramTable.Table.Cursor() == point)
 		paramStyle.Layout(gtx)
 		return D{Size: image.Pt(gtx.Constraints.Max.X, gtx.Constraints.Max.Y)}
 	}
@@ -351,63 +352,61 @@ func (t *UnitEditor) Tags(level int, yield TagYieldFunc) bool {
 	return yield(level, widget) && yield(level+1, &t.commentEditor.widgetEditor)
 }
 
-type ParameterWidget struct {
+type ParameterState struct {
 	knobState  KnobState
 	boolWidget widget.Bool
-	instrBtn   Clickable
-	instrMenu  MenuState
-	unitBtn    Clickable
-	unitMenu   MenuState
-	Parameter  tracker.Parameter
-	tipArea    TipArea
+	clickable  Clickable
+	portState  PortState
 }
 
 type ParameterStyle struct {
-	tracker         *Tracker
-	w               *ParameterWidget
-	Theme           *Theme
-	SendTargetTheme *material.Theme
-	Focus           bool
+	Parameter tracker.Parameter
+	State     *ParameterState
+	Theme     *Theme
+	Focus     bool
 }
 
-func (t *Tracker) ParamStyle(th *Theme, paramWidget *ParameterWidget) ParameterStyle {
-	sendTargetTheme := th.Material.WithPalette(material.Palette{
-		Bg:         th.Material.Bg,
-		Fg:         th.UnitEditor.SendTarget,
-		ContrastBg: th.Material.ContrastBg,
-		ContrastFg: th.Material.ContrastFg,
-	})
+func (t *Tracker) ParamStyle(Parameter tracker.Parameter, th *Theme, paramWidget *ParameterState, focus bool) ParameterStyle {
 	return ParameterStyle{
-		tracker:         t, // TODO: we need this to pull the instrument names for ID style parameters, find out another way
-		Theme:           th,
-		SendTargetTheme: &sendTargetTheme,
-		w:               paramWidget,
+		Theme:     th,
+		State:     paramWidget,
+		Parameter: Parameter,
+		Focus:     focus,
 	}
 }
 
 func (p ParameterStyle) Layout(gtx C) D {
 	//_, _ := p.w.Parameter.Info()
-	title := Label(p.Theme, &p.Theme.UnitEditor.Name, p.w.Parameter.Name())
+	title := Label(p.Theme, &p.Theme.UnitEditor.Name, p.Parameter.Name())
+	t := TrackerFromContext(gtx)
 	widget := func(gtx C) D {
-		switch p.w.Parameter.Type() {
+		if port, ok := p.Parameter.Port(); t.IsChoosingSendTarget() && ok {
+			for p.State.portState.Clicked(gtx) {
+				t.ChooseSendTarget(p.Parameter.UnitID(), port).Do()
+			}
+			k := Port(p.Theme, &p.State.portState)
+			return k.Layout(gtx)
+		}
+		switch p.Parameter.Type() {
 		case tracker.IntegerParameter:
-			k := Knob(p.w.Parameter, p.Theme, &p.w.knobState, p.w.Parameter.Hint().Label, p.Focus)
+			k := Knob(p.Parameter, p.Theme, &p.State.knobState, p.Parameter.Hint().Label, p.Focus)
 			return k.Layout(gtx)
 		case tracker.BoolParameter:
-			ra := p.w.Parameter.Range()
-			p.w.boolWidget.Value = p.w.Parameter.Value() > ra.Min
-			boolStyle := material.Switch(&p.Theme.Material, &p.w.boolWidget, "Toggle boolean parameter")
+			ra := p.Parameter.Range()
+			p.State.boolWidget.Value = p.Parameter.Value() > ra.Min
+			boolStyle := material.Switch(&p.Theme.Material, &p.State.boolWidget, "Toggle boolean parameter")
 			boolStyle.Color.Disabled = p.Theme.Material.Fg
 			defer pointer.PassOp{}.Push(gtx.Ops).Pop()
 			dims := layout.Center.Layout(gtx, boolStyle.Layout)
-			if p.w.boolWidget.Value {
-				p.w.Parameter.SetValue(ra.Max)
+			if p.State.boolWidget.Value {
+				p.Parameter.SetValue(ra.Max)
 			} else {
-				p.w.Parameter.SetValue(ra.Min)
+				p.Parameter.SetValue(ra.Min)
 			}
 			return dims
 		case tracker.IDParameter:
-			return drawCircle(gtx, gtx.Dp(p.Theme.Knob.Diameter), p.Theme.Knob.Pos.Bg)
+			btn := ActionBtn(t.ChooseSendSource(p.Parameter.UnitID()), t.Theme, &p.State.clickable, "Set", p.Parameter.Hint().Label)
+			return btn.Layout(gtx)
 			/*instrItems := make([]ActionMenuItem, p.tracker.Instruments().Count())
 			for i := range instrItems {
 				i := i
@@ -449,6 +448,10 @@ func (p ParameterStyle) Layout(gtx C) D {
 				}),
 			)*/
 		}
+		if _, ok := p.Parameter.Port(); ok {
+			k := Port(p.Theme, &p.State.portState)
+			return k.Layout(gtx)
+		}
 		return D{}
 	}
 	title.Layout(gtx)
diff --git a/tracker/model.go b/tracker/model.go
index 7766b9d..42e8089 100644
--- a/tracker/model.go
+++ b/tracker/model.go
@@ -240,6 +240,7 @@ func (m *Model) change(kind string, t ChangeType, severity ChangeSeverity) func(
 				m.d.UnitIndex2 = clamp(m.d.UnitIndex2, 0, unitCount-1)
 				m.d.UnitSearching = false // if we change anything in the patch, reset the unit searching
 				m.d.UnitSearchString = ""
+				m.d.SendSource = 0
 				m.updateDerivedPatchData()
 				TrySend(m.broker.ToPlayer, any(m.d.Song.Patch.Copy()))
 			}
diff --git a/tracker/params.go b/tracker/params.go
index 400cc23..eff7ca8 100644
--- a/tracker/params.go
+++ b/tracker/params.go
@@ -20,6 +20,7 @@ type (
 		up     *sointu.UnitParameter
 		index  int
 		vtable parameterVtable
+		port   int
 	}
 
 	parameterVtable interface {
@@ -70,6 +71,12 @@ func (p *Parameter) Value() int {
 	}
 	return p.vtable.Value(p)
 }
+func (p *Parameter) Port() (int, bool) {
+	if p.port <= 0 {
+		return 0, false
+	}
+	return p.port - 1, true
+}
 func (p *Parameter) SetValue(value int) bool {
 	if p.vtable == nil {
 		return false
@@ -123,6 +130,12 @@ func (p *Parameter) Reset() {
 	}
 	p.vtable.Reset(p)
 }
+func (p *Parameter) UnitID() int {
+	if p.unit == nil {
+		return 0
+	}
+	return p.unit.ID
+}
 
 //
 
@@ -212,6 +225,9 @@ func (n *namedParameter) Range(p *Parameter) IntRange {
 	return IntRange{Min: p.up.MinValue, Max: p.up.MaxValue}
 }
 func (n *namedParameter) Type(p *Parameter) ParameterType {
+	if p.up == nil || !p.up.CanSet {
+		return NoParameter
+	}
 	if p.unit.Type == "send" && p.up.Name == "target" {
 		return IDParameter
 	}