diff --git a/cpp/src/core.gyp b/cpp/src/core.gyp
index 7c6570d..780b3f3 100644
--- a/cpp/src/core.gyp
+++ b/cpp/src/core.gyp
@@ -11,6 +11,7 @@
         'fm_op_kernel.cc',
         'freqlut.cc',
         'lfo.cc',
+        'log2.cc',
         'patch.cc',
         'pitchenv.cc',
         'resofilter.cc',
diff --git a/cpp/src/log2.cc b/cpp/src/log2.cc
new file mode 100644
index 0000000..7639613
--- /dev/null
+++ b/cpp/src/log2.cc
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2013 Google Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <math.h>
+
+#include "synth.h"
+#include "log2.h"
+
+int32_t log2tab[LOG2_N_SAMPLES << 1];
+
+void Log2::init() {
+  const double mul = 1 / log(2);
+  for (int i = 0; i < LOG2_N_SAMPLES; i++) {
+    double y = mul * log(i + (LOG2_N_SAMPLES)) + (7 - LOG2_LG_N_SAMPLES);
+    log2tab[(i << 1) + 1] = (int32_t)floor(y * (1 << 24) + 0.5);
+  }
+  for (int i = 0; i < LOG2_N_SAMPLES - 1; i++) {
+    log2tab[i << 1] = log2tab[(i << 1) + 3] - log2tab[(i << 1) + 1];
+  }
+  log2tab[(LOG2_N_SAMPLES << 1) - 2] = (8 << 24) - log2tab[(LOG2_N_SAMPLES << 1) - 1];
+}
+
diff --git a/cpp/src/log2.h b/cpp/src/log2.h
new file mode 100644
index 0000000..998e0d5
--- /dev/null
+++ b/cpp/src/log2.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright 2013 Google Inc.
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+class Log2 {
+ public:
+  Log2();
+
+  static void init();
+
+  // Q24 in, Q24 out
+  static int32_t lookup(uint32_t x);
+};
+
+#define LOG2_LG_N_SAMPLES 9
+#define LOG2_N_SAMPLES (1 << LOG2_LG_N_SAMPLES)
+
+#define LOG2_INLINE
+
+extern int32_t log2tab[LOG2_N_SAMPLES << 1];
+
+#ifdef __GNUC__
+static int clz(unsigned int x) {
+  return __builtin_clz(x);
+}
+// TODO: other implementations (including ANSI C)
+#endif
+
+#ifdef LOG2_INLINE
+inline
+int32_t Log2::lookup(uint32_t x) {
+  int exp = clz(x | 1);
+  unsigned int y = x << exp;
+
+  const int SHIFT = 31 - LOG2_LG_N_SAMPLES;
+  int lowbits = y & ((1 << SHIFT) - 1);
+  int y_int = (y >> (SHIFT - 1)) & ((LOG2_N_SAMPLES - 1) << 1);
+  int dz = log2tab[y_int];
+  int z0 = log2tab[y_int + 1];
+
+  int z = z0 + (((int64_t)dz * (int64_t)lowbits) >> SHIFT);
+  return z - (exp << 24);
+}
+#endif
diff --git a/cpp/src/main.cc b/cpp/src/main.cc
index f3be631..e20ca8a 100644
--- a/cpp/src/main.cc
+++ b/cpp/src/main.cc
@@ -25,10 +25,13 @@
 #include "sawtooth.h"
 #include "sin.h"
 #include "exp2.h"
+#include "log2.h"
 #include "resofilter.h"
 #include "fm_core.h"
 #include "fm_op_kernel.h"
 #include "env.h"
+#include "patch.h"
+#include "controllers.h"
 #include "dx7note.h"
 
 using namespace std;
@@ -60,7 +63,22 @@ void test_sin_accuracy() {
     double err = fabs(y - yd);
     if (err > maxerr) maxerr = err;
   }
-  cout << "Max error: " << maxerr;
+  cout << "Max error: " << maxerr << endl;
+}
+
+void test_log_accuracy() {
+  double maxerr = 0;
+  for (int i = 0; i < 1000000; i++) {
+    uint32_t x = rand();
+    int32_t y = Log2::lookup(x);
+    double yd = (1 << 24) * log(x * (1.0 / (1 << 24))) / log(2);
+    double err = fabs(y - yd);
+    if (err > maxerr) {
+      maxerr = err;
+      cout << "x = " << x << ", y = " << y << ", yd = " << (int)yd << endl;
+    }
+  }
+  cout << "Max error: " << maxerr << endl;
 }
 
 void test_pure_accuracy() {
@@ -197,7 +215,12 @@ void mkdx7note(double sample_rate) {
   const int n_samples = 400 * 1024;
   WavOut w("/tmp/foo.wav", sample_rate, n_samples);
 
-  Dx7Note note(epiano, 57, 64);
+  Dx7Note note;
+  char unpacked_patch[156];
+  UnpackPatch(epiano, unpacked_patch);
+  note.init(unpacked_patch, 57, 64);
+  Controllers controllers;
+  controllers.values_[kControllerPitch] = 0x2000;
   int32_t buf[N];
 
   for (int i = 0; i < n_samples; i += N) {
@@ -207,7 +230,7 @@ void mkdx7note(double sample_rate) {
     if (i == n_samples / 2) {
       note.keyup();
     }
-     note.compute(buf);
+     note.compute(buf, 0, 0, &controllers);
     for (int j = 0; j < N; j++) {
       buf[j] >>= 2;
     }
@@ -236,17 +259,19 @@ int main(int argc, char **argv) {
   Sawtooth::init(sample_rate);
   Sin::init();
   Exp2::init();
+  Log2::init();
 
   //FmCore::dump();
   //test_sin_accuracy();
+  test_log_accuracy();
   //benchmark_fm_op();
   //test_pure_accuracy();
   //benchmark_sin();
   //int32_t freq = atoi(argv[1]);
   //cout << "Logfreq(" << freq << ") = " << Freqlut::lookup(freq) << endl;
 
-  //mkdx7note(sample_rate);
-  mksaw(sample_rate);
+  mkdx7note(sample_rate);
+  //mksaw(sample_rate);
   //test_ringbuffer();
   test_exp2();
   return 0;