diff --git a/go4k/cmd/sointu-tracker/main.go b/go4k/cmd/sointu-tracker/main.go
index 1cc2284..904c796 100644
--- a/go4k/cmd/sointu-tracker/main.go
+++ b/go4k/cmd/sointu-tracker/main.go
@@ -4,17 +4,24 @@ import (
 	"fmt"
 	"gioui.org/app"
 	"gioui.org/unit"
+	"github.com/vsariola/sointu/go4k/audio/oto"
 	"github.com/vsariola/sointu/go4k/tracker"
 	"os"
 )
 
 func main() {
+	plr, err := oto.NewPlayer()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(1)
+	}
+	defer plr.Close()
 	go func() {
 		w := app.NewWindow(
 			app.Size(unit.Dp(800), unit.Dp(600)),
 			app.Title("Sointu Tracker"),
 		)
-		if err := tracker.New().Run(w); err != nil {
+		if err := tracker.New(plr).Run(w); err != nil {
 			fmt.Println(err)
 			os.Exit(1)
 		}
diff --git a/go4k/tracker/keyevent.go b/go4k/tracker/keyevent.go
index c69309f..c234216 100644
--- a/go4k/tracker/keyevent.go
+++ b/go4k/tracker/keyevent.go
@@ -50,6 +50,9 @@ func (t *Tracker) KeyEvent(e key.Event) bool {
 		switch e.Name {
 		case key.NameEscape:
 			os.Exit(0)
+		case "Space":
+			t.TogglePlay()
+			return true
 		case key.NameUpArrow:
 			t.CursorRow = (t.CursorRow + t.song.PatternRows() - 1) % t.song.PatternRows()
 			return true
diff --git a/go4k/tracker/layout.go b/go4k/tracker/layout.go
index fdf66fa..883c96b 100644
--- a/go4k/tracker/layout.go
+++ b/go4k/tracker/layout.go
@@ -19,6 +19,7 @@ func (t *Tracker) layoutTracker(gtx layout.Context) layout.Dimensions {
 			t.ActiveTrack == i,
 			t.CursorRow,
 			t.CursorColumn,
+			int(t.PlayRow),
 		)))
 	}
 	return layout.Flex{Axis: layout.Horizontal}.Layout(gtx,
diff --git a/go4k/tracker/run.go b/go4k/tracker/run.go
index 6e4dab0..cfb547e 100644
--- a/go4k/tracker/run.go
+++ b/go4k/tracker/run.go
@@ -13,6 +13,8 @@ func (t *Tracker) Run(w *app.Window) error {
 	var ops op.Ops
 	for {
 		select {
+		case <-t.ticked:
+			w.Invalidate()
 		case e := <-w.Events():
 			switch e := e.(type) {
 			case system.DestroyEvent:
diff --git a/go4k/tracker/sequencer.go b/go4k/tracker/sequencer.go
new file mode 100644
index 0000000..2998dab
--- /dev/null
+++ b/go4k/tracker/sequencer.go
@@ -0,0 +1,87 @@
+package tracker
+
+import (
+	"fmt"
+	"sync/atomic"
+	"time"
+)
+
+func (t *Tracker) TogglePlay() {
+	t.Playing = !t.Playing
+	t.setPlaying <- t.Playing
+}
+
+// sequencerLoop is the main goroutine that handles the playing logic
+func (t *Tracker) sequencerLoop() {
+	playing := false
+	rowTime := (time.Second * 60) / time.Duration(4*t.song.BPM)
+	tick := make(<-chan time.Time)
+	curVoices := make([]int, len(t.song.Tracks))
+	for i := range curVoices {
+		curVoices[i] = t.song.FirstTrackVoice(i)
+	}
+	for {
+		select {
+		case <-tick:
+			next := time.Now().Add(rowTime)
+			pattern := atomic.LoadInt32(&t.PlayPattern)
+			row := atomic.LoadInt32(&t.PlayRow)
+			if int(row+1) == t.song.PatternRows() {
+				if int(pattern+1) == t.song.SequenceLength() {
+					atomic.StoreInt32(&t.PlayPattern, 0)
+				} else {
+					atomic.AddInt32(&t.PlayPattern, 1)
+				}
+				atomic.StoreInt32(&t.PlayRow, 0)
+			} else {
+				atomic.AddInt32(&t.PlayRow, 1)
+			}
+			if playing {
+				tick = time.After(next.Sub(time.Now()))
+			}
+			t.playRow(curVoices)
+			t.ticked <- struct{}{}
+		// TODO: maybe refactor the controls to be nicer, somehow?
+		case rowJump := <-t.rowJump:
+			atomic.StoreInt32(&t.PlayRow, int32(rowJump))
+		case patternJump := <-t.patternJump:
+			atomic.StoreInt32(&t.PlayPattern, int32(patternJump))
+		case playState := <-t.setPlaying:
+			playing = playState
+			if playing {
+				t.playBuffer = make([]float32, t.song.SamplesPerRow())
+				tick = time.After(0)
+			}
+		}
+	}
+}
+
+// playRow renders and writes the current row
+func (t *Tracker) playRow(curVoices []int) {
+	pattern := atomic.LoadInt32(&t.PlayPattern)
+	row := atomic.LoadInt32(&t.PlayRow)
+	for i, trk := range t.song.Tracks {
+		patternIndex := trk.Sequence[pattern]
+		note := t.song.Patterns[patternIndex][row]
+		if note == 1 { // anything but hold causes an action.
+			continue // TODO: can hold be actually something else than 1?
+		}
+		t.synth.Release(curVoices[i])
+		if note > 1 {
+			curVoices[i]++
+			first := t.song.FirstTrackVoice(i)
+			if curVoices[i] >= first+trk.NumVoices {
+				curVoices[i] = first
+			}
+			t.synth.Trigger(curVoices[i], note)
+		}
+	}
+	buff := make([]float32, t.song.SamplesPerRow()*2)
+	rendered, timeAdvanced, _ := t.synth.Render(buff, t.song.SamplesPerRow())
+	err := t.player.Play(buff)
+	if err != nil {
+		fmt.Println("error playing: %w", err)
+	} else if timeAdvanced != t.song.SamplesPerRow() {
+		fmt.Println("rendered only", rendered, "/", timeAdvanced, "expected", t.song.SamplesPerRow())
+	}
+}
diff --git a/go4k/tracker/theme.go b/go4k/tracker/theme.go
index d3ca2df..812abcd 100644
--- a/go4k/tracker/theme.go
+++ b/go4k/tracker/theme.go
@@ -16,6 +16,7 @@ var dark = color.RGBA{R: 24, G: 40, B: 44, A: 255}
 var white = color.RGBA{R: 255, G: 255, B: 255, A: 255}
 var black = color.RGBA{R: 0, G: 0, B: 0, A: 255}
 var yellow = color.RGBA{R: 255, G: 255, B: 130, A: 255}
+var red = color.RGBA{R: 255, G: 0, B: 0, A: 255}
 
 var panelColor = neutral
 var panelShadeColor = dark
@@ -31,3 +32,4 @@ var trackerFont = fontCollection[6].Font
 var trackerFontSize = unit.Px(16)
 var trackerTextColor = white
 var trackerActiveTextColor = yellow
+var trackerPlayColor = red
diff --git a/go4k/tracker/track.go b/go4k/tracker/track.go
index 0e0cf32..4540b11 100644
--- a/go4k/tracker/track.go
+++ b/go4k/tracker/track.go
@@ -15,7 +15,7 @@ import (
 const trackRowHeight = 16
 const trackWidth = 100
 
-func (t *Tracker) layoutTrack(notes []byte, active bool, cursorRow, cursorCol int) layout.Widget {
+func (t *Tracker) layoutTrack(notes []byte, active bool, cursorRow, cursorCol, playingRow int) layout.Widget {
 	return func(gtx layout.Context) layout.Dimensions {
 		gtx.Constraints.Min.X = trackWidth
 		gtx.Constraints.Max.X = trackWidth
@@ -45,6 +45,9 @@ func (t *Tracker) layoutTrack(notes []byte, active bool, cursorRow, cursorCol in
 		}
 		op.Offset(f32.Pt(0, (-1*trackRowHeight)*float32(cursorRow))).Add(gtx.Ops)
 		for i, c := range notes {
+			if i == playingRow {
+				paint.FillShape(gtx.Ops, trackerPlayColor, clip.Rect{Max: image.Pt(trackWidth, trackRowHeight)}.Op())
+			}
 			if i == cursorRow {
 				paint.ColorOp{Color: trackerActiveTextColor}.Add(gtx.Ops)
 			} else {
diff --git a/go4k/tracker/tracker.go b/go4k/tracker/tracker.go
index e0037ce..7955d6d 100644
--- a/go4k/tracker/tracker.go
+++ b/go4k/tracker/tracker.go
@@ -1,8 +1,11 @@
 package tracker
 
 import (
+	"fmt"
 	"gioui.org/widget"
 	"github.com/vsariola/sointu/go4k"
+	"github.com/vsariola/sointu/go4k/audio"
+	"github.com/vsariola/sointu/go4k/bridge"
 )
 
 type Tracker struct {
@@ -11,14 +14,47 @@ type Tracker struct {
 	CursorRow      int
 	CursorColumn   int
 	DisplayPattern int
+	PlayPattern    int32
+	PlayRow        int32
 	ActiveTrack    int
 	CurrentOctave  byte
+	Playing        bool
+	ticked         chan struct{}
+	setPlaying     chan bool
+	rowJump        chan int
+	patternJump    chan int
+	player         audio.Player
+	synth          go4k.Synth
+	playBuffer     []float32
 }
 
-func New() *Tracker {
-	return &Tracker{
+func (t *Tracker) LoadSong(song go4k.Song) error {
+	if err := song.Validate(); err != nil {
+		return fmt.Errorf("invalid song: %w", err)
+	}
+	t.song = song
+	if synth, err := bridge.Synth(song.Patch); err != nil {
+		fmt.Println("error loading synth: %v", err)
+		t.synth = nil
+	} else {
+		t.synth = synth
+	}
+	return nil
+}
+
+func New(player audio.Player) *Tracker {
+	t := &Tracker{
 		QuitButton:    new(widget.Clickable),
 		CurrentOctave: 4,
-		song:          defaultSong,
+		player:        player,
+		setPlaying:    make(chan bool),
+		rowJump:       make(chan int),
+		patternJump:   make(chan int),
+		ticked:        make(chan struct{}),
 	}
+	go t.sequencerLoop()
+	if err := t.LoadSong(defaultSong); err != nil {
+		panic(fmt.Errorf("cannot load default song: %w", err))
+	}
+	return t
 }