diff --git a/.gitignore b/.gitignore
index a66be7a..7de4ab6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -48,8 +48,7 @@ sdcard
 .vscode/
 
 # temporary tests
-src/test/*.bin
+src/test/bin/
 src/test/objects/
 src/test/results/
-src/test/*.csv
 *xtleak.kcg*
diff --git a/src/fx_engine.hpp b/src/fx_engine.hpp
index a8b50a9..a3f2f91 100644
--- a/src/fx_engine.hpp
+++ b/src/fx_engine.hpp
@@ -11,6 +11,8 @@
 
 #include "fx_components.h"
 
+#define STEP_UP(x) x
+
 enum Format
 {
     FORMAT_12_BIT,
@@ -369,7 +371,7 @@ public:
         {
             for(unsigned i = 0; i < LFOIndex::kLFOCount; ++i) 
             {
-                c->lfo_value_[i] = this->lfo_[i]->process();
+                c->lfo_value_[i] = STEP_UP(this->lfo_[i]->process());
             }
         }
     }
diff --git a/src/fx_shimmer_reverb.cpp b/src/fx_shimmer_reverb.cpp
index ce13c56..9c0d490 100644
--- a/src/fx_shimmer_reverb.cpp
+++ b/src/fx_shimmer_reverb.cpp
@@ -10,7 +10,9 @@ ShimmerReverb::ShimmerReverb(float32_t sampling_rate) :
     engine_(sampling_rate),
     input_gain_(-1.0f),
     diffusion_(-1.0f),
-    lp_(-1.0f)
+    lp_(-1.0f),
+    lp_decay_1_(0.0f),
+    lp_decay_2_(0.0f)
 {
     this->engine_.setLFOFrequency(Engine::LFOIndex::LFO_1, 0.5f);
     this->engine_.setLFOFrequency(Engine::LFOIndex::LFO_2, 0.3f);
@@ -27,6 +29,8 @@ ShimmerReverb::~ShimmerReverb()
 void ShimmerReverb::reset()
 {
     this->engine_.reset();
+    this->lp_decay_1_ = 0.0f;
+    this->lp_decay_2_ = 0.0f;
 }
 
 void ShimmerReverb::processSample(float32_t inL, float32_t inR, float32_t& outL, float32_t& outR)
@@ -96,7 +100,7 @@ void ShimmerReverb::processSample(float32_t inL, float32_t inR, float32_t& outL,
     c.write(del1, 2.0f);
     c.write(wet, 0.0f);
 
-    outR = wet;
+    outL = wet;
 
     c.load(apout);
     c.interpolate(del1, 4450.0f, Engine::LFOIndex::LFO_1, 50.0f, krt);
diff --git a/src/test/Makefile b/src/test/Makefile
index 58ab5ac..0df43b0 100644
--- a/src/test/Makefile
+++ b/src/test/Makefile
@@ -1,7 +1,9 @@
+BINDIR := bin
 OBJDIR := objects
-OUTPUT_FOLDER = results
-EXE := all_test.bin
-BETA := beta.bin
+OUTPUT_FOLDER := results
+
+EXE := $(BINDIR)/all_test.bin
+BETA := $(BINDIR)/beta.bin
 
 CXX := g++
 CXXFLAGS = 	-g -std=c++20 -MMD -MP
@@ -44,7 +46,7 @@ BETAOBJS = $(BETASRCS:%.cpp=$(OBJDIR)/%.o)
 
 all: $(EXE) test
 
-bin: $(EXE)
+build: $(EXE)
 
 test: $(EXE) $(OUTPUT_FOLDER)
 	rm -rf $(OUTPUT_FOLDER)/*
@@ -54,6 +56,9 @@ test-debug: $(EXE) $(OUTPUT_FOLDER)
 	rm -rf $(OUTPUT_FOLDER)/*
 	valgrind --leak-check=full --leak-resolution=high --show-leak-kinds=all --xtree-leak=yes --show-mismatched-frees=yes --error-limit=no --log-file=$(OUTPUT_FOLDER)/valgrind-analysis-results.txt ./$(EXE)
 
+$(BINDIR):
+	mkdir -p $@
+
 $(OBJDIR):
 	mkdir -p $@
 
@@ -66,11 +71,11 @@ $(OBJDIR)/%.o: %.cpp $(OBJDIR)
 $(OBJDIR)/%.o: ../%.cpp $(OBJDIR)
 	$(CXX) $(CXXFLAGS) $(DEFINES) $(INCLUDES) -c $< -o $@
 
-$(EXE): $(TST_OBJS) $(FX__OBJS)
+$(EXE): $(BINDIR) $(TST_OBJS) $(FX__OBJS)
 	$(LD) $(CXXFLAGS) $(call wildcard,$(TST_OBJS)) $(call wildcard,$(FX__OBJS)) -o $@ $(LIBS)
 
-$(BETA): $(BETAOBJS) beta.cpp
+$(BETA): $(BINDIR) $(BETAOBJS) $(FX__OBJS)
 	$(LD) $(CXXFLAGS) $(BETAOBJS) $(call wildcard,$(FX__OBJS)) -o $@ $(LIBS)
 
 clean:
-	rm -rf *.o $(OBJDIR) $(EXE) $(OUTPUT_FOLDER)
+	rm -rf $(OBJDIR) $(BINDIR) $(OUTPUT_FOLDER)
diff --git a/src/test/lowlevel.cpp b/src/test/lowlevel.cpp
new file mode 100644
index 0000000..1ba89ce
--- /dev/null
+++ b/src/test/lowlevel.cpp
@@ -0,0 +1,157 @@
+#include <gtest/gtest.h>
+
+#include <iostream>
+
+#include "test_fx_helper.h"
+#include "../fx_engine.hpp"
+
+#define EXEC_PRINT(ctx, x) \
+    std::cout.fill(' '); \
+    std::cout.width(80); \
+    std::cout << std::left; \
+    std::cout.precision(6); \
+    std::cout << std::fixed; \
+    std::cout << #x; \
+    x \
+    { \
+        float32_t v = 0.0f; \
+        ctx.write(v); \
+        std::cout << " // accumulator_: " << v; \
+    } \
+    std::cout << std::endl
+
+#define TAIL , -1
+
+typedef FxEngine<16384, Format::FORMAT_FLOAT32, true> Engine;
+
+void processShimmerSample(
+    Engine& engine_, size_t index, 
+    float32_t& lp_decay_1_, float32_t& lp_decay_2_, 
+    float32_t inL, float32_t inR, 
+    float32_t& outL, float32_t& outR)
+{
+    // This is the Griesinger topology described in the Dattorro paper
+    // (4 AP diffusers on the input, then a loop of 2x 2AP+1Delay).
+    // Modulation is applied in the loop of the first diffuser AP for additional
+    // smearing; and to the two long delays for a slow shimmer/chorus effect.
+    typedef Engine::Reserve< 113,
+            Engine::Reserve< 162,
+            Engine::Reserve< 241,
+            Engine::Reserve< 399,
+            Engine::Reserve<1653,
+            Engine::Reserve<2038,
+            Engine::Reserve<3411,
+            Engine::Reserve<1913,
+            Engine::Reserve<1663,
+            Engine::Reserve<4782> > > > > > > > > > Memory;
+    Engine::DelayLine<Memory, 0> ap1;
+    Engine::DelayLine<Memory, 1> ap2;
+    Engine::DelayLine<Memory, 2> ap3;
+    Engine::DelayLine<Memory, 3> ap4;
+    Engine::DelayLine<Memory, 4> dap1a;
+    Engine::DelayLine<Memory, 5> dap1b;
+    Engine::DelayLine<Memory, 6> del1;
+    Engine::DelayLine<Memory, 7> dap2a;
+    Engine::DelayLine<Memory, 8> dap2b;
+    Engine::DelayLine<Memory, 9> del2;
+    Engine::Context c;
+
+    const float32_t kap = 0.8f;
+    const float32_t klp = 0.7f;
+    const float32_t krt = 0.75f;
+    const float32_t gain = 0.55f;
+
+    float32_t lp_1 = lp_decay_1_;
+    float32_t lp_2 = lp_decay_2_;
+
+    float32_t wet = 0.0f;
+    float32_t apout = 0.0f;
+    engine_.start(&c);
+
+    // Smear AP1 inside the loop.
+    EXEC_PRINT(c, c.interpolate(ap1, 10.0f, Engine::LFOIndex::LFO_1, 60.0f, 1.0f););
+    EXEC_PRINT(c, c.write(ap1, 100, 0.0f););
+    EXEC_PRINT(c, c.read(inL, gain););
+
+    // Diffuse through 4 allpasses.
+    EXEC_PRINT(c, c.read(ap1 TAIL, kap););
+    EXEC_PRINT(c, c.writeAllPass(ap1, -kap););
+    EXEC_PRINT(c, c.read(ap2 TAIL, kap););
+    EXEC_PRINT(c, c.writeAllPass(ap2, -kap););
+    EXEC_PRINT(c, c.read(ap3 TAIL, kap););
+    EXEC_PRINT(c, c.writeAllPass(ap3, -kap););
+    EXEC_PRINT(c, c.read(ap4 TAIL, kap););
+    EXEC_PRINT(c, c.writeAllPass(ap4, -kap););
+    EXEC_PRINT(c, c.write(apout););
+      
+    // Main reverb loop.
+    EXEC_PRINT(c, c.load(apout););
+    EXEC_PRINT(c, c.interpolate(del2, 4680.0f, Engine::LFOIndex::LFO_2, 100.0f, krt););
+    EXEC_PRINT(c, c.lp(lp_1, klp););
+    EXEC_PRINT(c, c.read(dap1a TAIL, -kap););
+    EXEC_PRINT(c, c.writeAllPass(dap1a, kap););
+    EXEC_PRINT(c, c.read(dap1b TAIL, kap););
+    EXEC_PRINT(c, c.writeAllPass(dap1b, -kap););
+    EXEC_PRINT(c, c.write(del1, 2.0f););
+    EXEC_PRINT(c, c.write(wet, 0.0f););
+
+    outL = wet;
+
+
+    EXEC_PRINT(c, c.load(apout););
+    EXEC_PRINT(c, c.interpolate(del1, 4450.0f, Engine::LFOIndex::LFO_1, 50.0f, krt););
+    EXEC_PRINT(c, c.read(del1 TAIL, krt););
+    EXEC_PRINT(c, c.lp(lp_2, klp););
+    EXEC_PRINT(c, c.read(dap2a TAIL, kap););
+    EXEC_PRINT(c, c.writeAllPass(dap2a, -kap););
+    EXEC_PRINT(c, c.read(dap2b TAIL, -kap););
+    EXEC_PRINT(c, c.writeAllPass(dap2b, kap););
+    EXEC_PRINT(c, c.write(del2, 2.0f););
+    EXEC_PRINT(c, c.write(wet, 0.0f););
+
+    outR = wet;
+
+    std::cout << "Index # " << index << " - ( " << inL << ", " << inR << " ) ==> ( " << outL << ", " << outR << " )" << std::endl;
+    std::cout << std::endl << "**********************************************************************************************************" << std::endl << std::endl;
+
+    lp_decay_1_ = lp_1;
+    lp_decay_2_ = lp_2;
+}
+
+TEST(LowLevel, TestShimmerAlgo)
+{
+    const testing::TestInfo* test_info = testing::UnitTest::GetInstance()->current_test_info();
+    std::string full_test_name = test_info->test_case_name();
+    full_test_name += ".";
+    full_test_name += test_info->name();
+
+    Engine engine_(SAMPLING_FREQUENCY);
+    engine_.setLFOFrequency(Engine::LFOIndex::LFO_1, 0.5f);
+    engine_.setLFOFrequency(Engine::LFOIndex::LFO_2, 0.3f);
+    engine_.reset();
+
+    float32_t lp1 = 0.0f;
+    float32_t lp2 = 0.0f;
+
+    const size_t size = static_cast<float32_t>(SAMPLING_FREQUENCY);
+    float32_t* inSamples = new float32_t[size];
+    memset(inSamples, 0, size * sizeof(float32_t));
+    inSamples[0] = 1.0f;
+
+    float32_t* outSamplesL = new float32_t[size];
+    float32_t* outSamplesR = new float32_t[size];
+    memset(outSamplesL, 0, size * sizeof(float32_t));
+    memset(outSamplesR, 0, size * sizeof(float32_t));
+
+    for(size_t i = 0; i < size; ++i)
+    {
+        processShimmerSample(engine_, i, lp1, lp2, inSamples[i], inSamples[i], outSamplesL[i], outSamplesR[i]);
+    }
+
+    saveWaveFile(getResultFile(full_test_name + ".wav", true), outSamplesL, outSamplesR, size, SAMPLING_FREQUENCY, 16);
+
+    delete[] outSamplesL;
+    delete[] outSamplesR;
+
+    delete[] inSamples;
+}