diff --git a/synth/config.go b/synth/config.go
index 67fcb2b..7636102 100644
--- a/synth/config.go
+++ b/synth/config.go
@@ -11,6 +11,53 @@ const (
 	WhisperFloor     = 0.03                               // D-08/D-09: 3% of max amplitude
 )
 
+// WaveformType selects the harmonic preset for a synthesis layer.
+// The zero value WaveformCustom preserves existing hand-tuned harmonics in FreqConfig.Harmonics.
+type WaveformType int
+
+const (
+	WaveformCustom   WaveformType = iota // zero value: use FreqConfig.Harmonics as-is
+	WaveformSine                         // pure fundamental, single harmonic
+	WaveformSquare                       // odd harmonics with 1/k amplitude (bandlimited)
+	WaveformSawtooth                     // all harmonics with 1/k amplitude (bandlimited)
+	WaveformTriangle                     // odd harmonics with alternating 1/k^2 amplitude (bandlimited)
+)
+
+// WaveformPresetHarmonics returns the bandlimited harmonic series for the given waveform type
+// at the given base frequency and sample rate. Returns nil for WaveformCustom.
+// All returned harmonics are below Nyquist (sampleRate/2).
+func WaveformPresetHarmonics(wt WaveformType, baseHz float64, sampleRate int) []HarmonicDef {
+	nyquist := float64(sampleRate) / 2.0
+	switch wt {
+	case WaveformCustom:
+		return nil
+	case WaveformSine:
+		return []HarmonicDef{{Ratio: 1, Amplitude: 1.0}}
+	case WaveformSquare:
+		var harmonics []HarmonicDef
+		for k := 1; float64(k)*baseHz < nyquist; k += 2 {
+			harmonics = append(harmonics, HarmonicDef{Ratio: k, Amplitude: 1.0 / float64(k)})
+		}
+		return harmonics
+	case WaveformSawtooth:
+		var harmonics []HarmonicDef
+		for k := 1; float64(k)*baseHz < nyquist; k++ {
+			harmonics = append(harmonics, HarmonicDef{Ratio: k, Amplitude: 1.0 / float64(k)})
+		}
+		return harmonics
+	case WaveformTriangle:
+		var harmonics []HarmonicDef
+		sign := 1.0
+		for k := 1; float64(k)*baseHz < nyquist; k += 2 {
+			harmonics = append(harmonics, HarmonicDef{Ratio: k, Amplitude: sign / float64(k*k)})
+			sign = -sign
+		}
+		return harmonics
+	default:
+		return nil
+	}
+}
+
 // HarmonicDef defines one partial in an additive synthesizer.
 type HarmonicDef struct {
 	Ratio     int     // harmonic number: 1=fundamental, 2=octave, 3=fifth+octave, etc.
@@ -19,29 +66,30 @@ type HarmonicDef struct {
 
 // FreqConfig holds synthesis parameters for one traffic class.
 type FreqConfig struct {
-	BaseHz    float64
-	Harmonics []HarmonicDef
-	Pan       float64 // [-1, 1]: -1=full left, 0=center, +1=full right
+	BaseHz       float64
+	Harmonics    []HarmonicDef
+	Pan          float64      // [-1, 1]: -1=full left, 0=center, +1=full right
+	WaveformType WaveformType // zero value WaveformCustom uses Harmonics as-is
 }
 
 // ClassFreqConfigs maps each traffic class to its synthesis parameters.
 // Frequencies use musical intervals per D-02/D-03. Harmonics per D-05/D-06.
 // Pan positions per D-12.
 var ClassFreqConfigs = map[classify.TrafficClass]FreqConfig{
-	classify.ClassICMP:     {65.0, []HarmonicDef{{1, 1.0}, {2, 0.4}, {3, 0.15}}, 0.0},
-	classify.ClassDNS:      {110.0, []HarmonicDef{{1, 1.0}, {2, 0.5}, {3, 0.25}}, -0.2},
-	classify.ClassHTTPS:    {175.0, []HarmonicDef{{1, 1.0}, {2, 0.6}, {3, 0.3}}, 0.2},
-	classify.ClassHTTP:     {220.0, []HarmonicDef{{1, 1.0}, {2, 0.5}, {4, 0.2}}, -0.35},
-	classify.ClassSSH:      {330.0, []HarmonicDef{{1, 1.0}, {3, 0.6}, {5, 0.3}}, 0.35},
-	classify.ClassSMTP:     {440.0, []HarmonicDef{{1, 1.0}, {2, 0.3}, {3, 0.1}}, -0.55},
-	classify.ClassNTP:      {520.0, []HarmonicDef{{1, 1.0}, {2, 0.25}}, 0.55},
-	classify.ClassDHCP:     {600.0, []HarmonicDef{{1, 1.0}, {2, 0.35}, {3, 0.15}}, -0.75},
-	classify.ClassOtherTCP: {700.0, []HarmonicDef{{1, 1.0}, {2, 0.2}}, 0.75},
-	classify.ClassOtherUDP: {780.0, []HarmonicDef{{1, 1.0}, {2, 0.2}}, -0.75},
+	classify.ClassICMP:     {BaseHz: 65.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.4}, {3, 0.15}}, Pan: 0.0},
+	classify.ClassDNS:      {BaseHz: 110.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.5}, {3, 0.25}}, Pan: -0.2},
+	classify.ClassHTTPS:    {BaseHz: 175.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.6}, {3, 0.3}}, Pan: 0.2},
+	classify.ClassHTTP:     {BaseHz: 220.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.5}, {4, 0.2}}, Pan: -0.35},
+	classify.ClassSSH:      {BaseHz: 330.0, Harmonics: []HarmonicDef{{1, 1.0}, {3, 0.6}, {5, 0.3}}, Pan: 0.35},
+	classify.ClassSMTP:     {BaseHz: 440.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.3}, {3, 0.1}}, Pan: -0.55},
+	classify.ClassNTP:      {BaseHz: 520.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.25}}, Pan: 0.55},
+	classify.ClassDHCP:     {BaseHz: 600.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.35}, {3, 0.15}}, Pan: -0.75},
+	classify.ClassOtherTCP: {BaseHz: 700.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.2}}, Pan: 0.75},
+	classify.ClassOtherUDP: {BaseHz: 780.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.2}}, Pan: -0.75},
 	// D-05: Unknown buckets in 850-1100 Hz dissonant range, detuned intervals
 	// D-06: Same dissonant harmonic character {1,1.0},{2,0.8},{3,0.4} for all 4
-	classify.ClassUnknown1: {862.0, []HarmonicDef{{1, 1.0}, {2, 0.8}, {3, 0.4}}, 0.6},
-	classify.ClassUnknown2: {920.0, []HarmonicDef{{1, 1.0}, {2, 0.8}, {3, 0.4}}, -0.6},
-	classify.ClassUnknown3: {981.0, []HarmonicDef{{1, 1.0}, {2, 0.8}, {3, 0.4}}, 0.9},
-	classify.ClassUnknown4: {1047.0, []HarmonicDef{{1, 1.0}, {2, 0.8}, {3, 0.4}}, -0.9},
+	classify.ClassUnknown1: {BaseHz: 862.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.8}, {3, 0.4}}, Pan: 0.6},
+	classify.ClassUnknown2: {BaseHz: 920.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.8}, {3, 0.4}}, Pan: -0.6},
+	classify.ClassUnknown3: {BaseHz: 981.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.8}, {3, 0.4}}, Pan: 0.9},
+	classify.ClassUnknown4: {BaseHz: 1047.0, Harmonics: []HarmonicDef{{1, 1.0}, {2, 0.8}, {3, 0.4}}, Pan: -0.9},
 }
diff --git a/synth/layer.go b/synth/layer.go
index a07d018..8ec0b63 100644
--- a/synth/layer.go
+++ b/synth/layer.go
@@ -20,7 +20,11 @@ type Layer struct {
 }
 
 // NewLayer creates a Layer for the given config using the specified sample rate and EMA time constant (tau in seconds).
+// If cfg.WaveformType is not WaveformCustom, harmonics are resolved from the preset at construction time.
 func NewLayer(cfg FreqConfig, sampleRate int, tau float64) *Layer {
+	if cfg.WaveformType != WaveformCustom {
+		cfg.Harmonics = WaveformPresetHarmonics(cfg.WaveformType, cfg.BaseHz, sampleRate)
+	}
 	return &Layer{
 		Config:  cfg,
 		Osc:     NewOscillator(cfg.BaseHz, sampleRate),
diff --git a/synth/waveform_test.go b/synth/waveform_test.go
new file mode 100644
index 0000000..cbfba02
--- /dev/null
+++ b/synth/waveform_test.go
@@ -0,0 +1,201 @@
+package synth_test
+
+import (
+	"testing"
+
+	"github.com/netsynth/netsynth/synth"
+)
+
+func TestWaveformPresetHarmonics_Sine(t *testing.T) {
+	harmonics := synth.WaveformPresetHarmonics(synth.WaveformSine, 440.0, 44100)
+	if len(harmonics) != 1 {
+		t.Fatalf("WaveformSine: expected 1 harmonic, got %d", len(harmonics))
+	}
+	if harmonics[0].Ratio != 1 {
+		t.Errorf("WaveformSine: expected Ratio=1, got %d", harmonics[0].Ratio)
+	}
+	if harmonics[0].Amplitude != 1.0 {
+		t.Errorf("WaveformSine: expected Amplitude=1.0, got %.4f", harmonics[0].Amplitude)
+	}
+}
+
+func TestWaveformPresetHarmonics_Square(t *testing.T) {
+	harmonics := synth.WaveformPresetHarmonics(synth.WaveformSquare, 440.0, 44100)
+	if len(harmonics) == 0 {
+		t.Fatal("WaveformSquare: expected at least one harmonic, got 0")
+	}
+	nyquist := 22050.0
+	for _, h := range harmonics {
+		if float64(h.Ratio)*440.0 >= nyquist {
+			t.Errorf("WaveformSquare: harmonic ratio %d exceeds Nyquist (freq=%.1f)", h.Ratio, float64(h.Ratio)*440.0)
+		}
+		expectedAmp := 1.0 / float64(h.Ratio)
+		if abs(h.Amplitude-expectedAmp) > 1e-9 {
+			t.Errorf("WaveformSquare: harmonic %d: expected amplitude %.6f, got %.6f", h.Ratio, expectedAmp, h.Amplitude)
+		}
+	}
+}
+
+func TestWaveformPresetHarmonics_Sawtooth(t *testing.T) {
+	harmonics := synth.WaveformPresetHarmonics(synth.WaveformSawtooth, 440.0, 44100)
+	if len(harmonics) == 0 {
+		t.Fatal("WaveformSawtooth: expected at least one harmonic, got 0")
+	}
+	nyquist := 22050.0
+	for _, h := range harmonics {
+		if float64(h.Ratio)*440.0 >= nyquist {
+			t.Errorf("WaveformSawtooth: harmonic ratio %d exceeds Nyquist (freq=%.1f)", h.Ratio, float64(h.Ratio)*440.0)
+		}
+		expectedAmp := 1.0 / float64(h.Ratio)
+		if abs(h.Amplitude-expectedAmp) > 1e-9 {
+			t.Errorf("WaveformSawtooth: harmonic %d: expected amplitude %.6f, got %.6f", h.Ratio, expectedAmp, h.Amplitude)
+		}
+	}
+}
+
+func TestWaveformPresetHarmonics_Triangle(t *testing.T) {
+	harmonics := synth.WaveformPresetHarmonics(synth.WaveformTriangle, 440.0, 44100)
+	if len(harmonics) == 0 {
+		t.Fatal("WaveformTriangle: expected at least one harmonic, got 0")
+	}
+	nyquist := 22050.0
+	sign := 1.0
+	for i, h := range harmonics {
+		if float64(h.Ratio)*440.0 >= nyquist {
+			t.Errorf("WaveformTriangle: harmonic ratio %d exceeds Nyquist (freq=%.1f)", h.Ratio, float64(h.Ratio)*440.0)
+		}
+		expectedAmp := sign / float64(h.Ratio*h.Ratio)
+		if abs(h.Amplitude-expectedAmp) > 1e-9 {
+			t.Errorf("WaveformTriangle: harmonic %d (index %d): expected amplitude %.6f, got %.6f", h.Ratio, i, expectedAmp, h.Amplitude)
+		}
+		sign = -sign
+	}
+}
+
+func TestWaveformPresetHarmonics_Custom(t *testing.T) {
+	harmonics := synth.WaveformPresetHarmonics(synth.WaveformCustom, 440.0, 44100)
+	if harmonics != nil {
+		t.Errorf("WaveformCustom: expected nil, got %v", harmonics)
+	}
+}
+
+func TestBandlimitedHarmonicsNoAliasing(t *testing.T) {
+	waveforms := []synth.WaveformType{
+		synth.WaveformSine,
+		synth.WaveformSquare,
+		synth.WaveformSawtooth,
+		synth.WaveformTriangle,
+	}
+	for _, cfg := range synth.ClassFreqConfigs {
+		for _, wt := range waveforms {
+			harmonics := synth.WaveformPresetHarmonics(wt, cfg.BaseHz, 44100)
+			for _, h := range harmonics {
+				freq := float64(h.Ratio) * cfg.BaseHz
+				if freq >= 22050.0 {
+					t.Errorf("waveform %d, baseHz=%.1f: harmonic ratio %d produces freq=%.1f >= Nyquist 22050", wt, cfg.BaseHz, h.Ratio, freq)
+				}
+			}
+		}
+	}
+}
+
+func TestWaveformPresetHarmonics_SquareOddOnly(t *testing.T) {
+	harmonics := synth.WaveformPresetHarmonics(synth.WaveformSquare, 440.0, 44100)
+	for _, h := range harmonics {
+		if h.Ratio%2 == 0 {
+			t.Errorf("WaveformSquare: found even ratio %d (should be odd-only)", h.Ratio)
+		}
+	}
+}
+
+func TestWaveformPresetHarmonics_TriangleOddOnly(t *testing.T) {
+	harmonics := synth.WaveformPresetHarmonics(synth.WaveformTriangle, 440.0, 44100)
+	for _, h := range harmonics {
+		if h.Ratio%2 == 0 {
+			t.Errorf("WaveformTriangle: found even ratio %d (should be odd-only)", h.Ratio)
+		}
+	}
+}
+
+func TestWaveformPresetHarmonics_SawtoothConsecutive(t *testing.T) {
+	harmonics := synth.WaveformPresetHarmonics(synth.WaveformSawtooth, 440.0, 44100)
+	for i, h := range harmonics {
+		expected := i + 1
+		if h.Ratio != expected {
+			t.Errorf("WaveformSawtooth: index %d: expected ratio %d, got %d", i, expected, h.Ratio)
+		}
+	}
+}
+
+func TestNewLayerResolvesWaveformPreset(t *testing.T) {
+	cfg := synth.FreqConfig{
+		BaseHz:       440.0,
+		WaveformType: synth.WaveformSquare,
+		// Harmonics intentionally empty — preset should be resolved
+	}
+	layer := synth.NewLayer(cfg, synth.SampleRate, 1.0)
+	if len(layer.Config.Harmonics) <= 1 {
+		t.Errorf("expected layer.Config.Harmonics to have length > 1 after preset resolution, got %d", len(layer.Config.Harmonics))
+	}
+	if layer.Config.Harmonics[0].Ratio != 1 {
+		t.Errorf("expected first harmonic Ratio=1, got %d", layer.Config.Harmonics[0].Ratio)
+	}
+}
+
+func TestNewLayerPreservesCustomHarmonics(t *testing.T) {
+	cfg := synth.FreqConfig{
+		BaseHz:    440.0,
+		Harmonics: []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}, {Ratio: 2, Amplitude: 0.4}},
+		// WaveformType zero value = WaveformCustom
+	}
+	layer := synth.NewLayer(cfg, synth.SampleRate, 1.0)
+	if len(layer.Config.Harmonics) != 2 {
+		t.Errorf("expected exactly 2 harmonics preserved, got %d", len(layer.Config.Harmonics))
+	}
+	if layer.Config.Harmonics[1].Amplitude != 0.4 {
+		t.Errorf("expected second harmonic Amplitude=0.4, got %.4f", layer.Config.Harmonics[1].Amplitude)
+	}
+}
+
+func TestSineRegressionVsCustomHarmonics(t *testing.T) {
+	// Sine preset should produce identical output to a single-harmonic custom config
+	cfgSine := synth.FreqConfig{
+		BaseHz:       440.0,
+		WaveformType: synth.WaveformSine,
+	}
+	cfgCustom := synth.FreqConfig{
+		BaseHz:    440.0,
+		Harmonics: []synth.HarmonicDef{{Ratio: 1, Amplitude: 1.0}},
+	}
+	// Use fast-converging tau for test
+	layerSine := synth.NewLayer(cfgSine, synth.SampleRate, 0.001)
+	layerCustom := synth.NewLayer(cfgCustom, synth.SampleRate, 0.001)
+
+	// Set both to same target amplitude
+	layerSine.UpdateTarget(1, 1)
+	layerCustom.UpdateTarget(1, 1)
+
+	// Advance enough samples for EMA to converge (tau=0.001 at 44100 SR: ~44 samples to 63%)
+	for i := 0; i < 200; i++ {
+		layerSine.AdvanceSample()
+		layerCustom.AdvanceSample()
+	}
+
+	// Next 100 samples should match exactly
+	for i := 0; i < 100; i++ {
+		s1 := layerSine.AdvanceSample()
+		s2 := layerCustom.AdvanceSample()
+		if abs(s1-s2) > 1e-12 {
+			t.Errorf("sample %d: sine preset (%.10f) != custom harmonic (%.10f), diff=%.2e", i, s1, s2, abs(s1-s2))
+			break
+		}
+	}
+}
+
+// abs returns the absolute value of x.
+func abs(x float64) float64 {
+	if x < 0 {
+		return -x
+	}
+	return x
+}