wip: synth api && adder

inc/Adder.h

@@ -0,0 +1,21 @@
+#pragma once
+#include <vector>
+#include "Oscillator.h"
+
+class Adder
+{
+private:
+    /* data */
+public:
+    Adder(/* args */);
+    ~Adder();
+    std::vector<float> & SumOscillators(const std::vector<Oscillator*> & oscillators, float duration);
+};
+
+Adder::Adder(/* args */)
+{
+}
+
+Adder::~Adder()
+{
+}