diff --git a/dlls/dsdmo/main.c b/dlls/dsdmo/main.c
index ff103be159e..57214b32752 100644
--- a/dlls/dsdmo/main.c
+++ b/dlls/dsdmo/main.c
@@ -438,6 +438,7 @@ struct eq
 {
     struct effect effect;
     IDirectSoundFXParamEq IDirectSoundFXParamEq_iface;
+    DSFXParamEq params;
 };
 
 static struct eq *impl_from_IDirectSoundFXParamEq(IDirectSoundFXParamEq *iface)
@@ -467,18 +468,24 @@ static HRESULT WINAPI eq_params_SetAllParameters(IDirectSoundFXParamEq *iface, c
 {
     struct eq *effect = impl_from_IDirectSoundFXParamEq(iface);
 
-    FIXME("effect %p, params %p, stub!\n", effect, params);
+    TRACE("effect %p, params %p.\n", effect, params);
 
-    return E_NOTIMPL;
+    EnterCriticalSection(&effect->effect.cs);
+    effect->params = *params;
+    LeaveCriticalSection(&effect->effect.cs);
+    return S_OK;
 }
 
 static HRESULT WINAPI eq_params_GetAllParameters(IDirectSoundFXParamEq *iface, DSFXParamEq *params)
 {
     struct eq *effect = impl_from_IDirectSoundFXParamEq(iface);
 
-    FIXME("effect %p, params %p, stub!\n", effect, params);
+    TRACE("effect %p, params %p.\n", effect, params);
 
-    return E_NOTIMPL;
+    EnterCriticalSection(&effect->effect.cs);
+    *params = effect->params;
+    LeaveCriticalSection(&effect->effect.cs);
+    return S_OK;
 }
 
 static const IDirectSoundFXParamEqVtbl eq_params_vtbl =
@@ -527,6 +534,10 @@ static HRESULT eq_create(IUnknown *outer, IUnknown **out)
     effect_init(&object->effect, outer, &eq_ops);
     object->IDirectSoundFXParamEq_iface.lpVtbl = &eq_params_vtbl;
 
+    object->params.fCenter = 8000.0f;
+    object->params.fBandwidth = 12.0f;
+    object->params.fGain = 0.0f;
+
     TRACE("Created equalizer effect %p.\n", object);
     *out = &object->effect.IUnknown_inner;
     return S_OK;
diff --git a/dlls/dsdmo/tests/dsdmo.c b/dlls/dsdmo/tests/dsdmo.c
index c59361e5fcf..1ecafeb7ceb 100644
--- a/dlls/dsdmo/tests/dsdmo.c
+++ b/dlls/dsdmo/tests/dsdmo.c
@@ -453,13 +453,27 @@ static void test_eq_parameters(void)
     ok(hr == S_OK, "Got hr %#x.\n", hr);
 
     hr = IDirectSoundFXParamEq_GetAllParameters(eq, &params);
-    todo_wine ok(hr == S_OK, "Got hr %#x.\n", hr);
-    if (hr == S_OK)
-    {
-        ok(params.fCenter == 8000.0f, "Got center frequency %.8e Hz.\n", params.fCenter);
-        ok(params.fBandwidth == 12.0f, "Got band width %.8e semitones.\n", params.fBandwidth);
-        ok(params.fGain == 0.0f, "Got gain %.8e.\n", params.fGain);
-    }
+    ok(hr == S_OK, "Got hr %#x.\n", hr);
+    ok(params.fCenter == 8000.0f, "Got center frequency %.8e Hz.\n", params.fCenter);
+    ok(params.fBandwidth == 12.0f, "Got band width %.8e semitones.\n", params.fBandwidth);
+    ok(params.fGain == 0.0f, "Got gain %.8e.\n", params.fGain);
+
+    params.fCenter = 79.0f;
+    hr = IDirectSoundFXParamEq_SetAllParameters(eq, &params);
+    todo_wine ok(hr == E_INVALIDARG, "Got hr %#x.\n", hr);
+    params.fCenter = 16001.0f;
+    hr = IDirectSoundFXParamEq_SetAllParameters(eq, &params);
+    todo_wine ok(hr == E_INVALIDARG, "Got hr %#x.\n", hr);
+    params.fCenter = 738.0f;
+    hr = IDirectSoundFXParamEq_SetAllParameters(eq, &params);
+    ok(hr == S_OK, "Got hr %#x.\n", hr);
+
+    memset(&params, 0xcc, sizeof(params));
+    hr = IDirectSoundFXParamEq_GetAllParameters(eq, &params);
+    ok(hr == S_OK, "Got hr %#x.\n", hr);
+    ok(params.fCenter == 738.0f, "Got center frequency %.8e Hz.\n", params.fCenter);
+    ok(params.fBandwidth == 12.0f, "Got band width %.8e semitones.\n", params.fBandwidth);
+    ok(params.fGain == 0.0f, "Got gain %.8e.\n", params.fGain);
 
     ref = IDirectSoundFXParamEq_Release(eq);
     ok(!ref, "Got outstanding refcount %d.\n", ref);