wip: filter lfo (still not worked)

inc/LFO.h

@@ -0,0 +1,20 @@
+#pragma once
+#include "Oscillator.h"
+
+class LFO: public Oscillator
+{
+private:
+    /* data */
+public:
+    LFO(/* args */);
+    ~LFO();
+    void SetFreq(float freq) { m_phase_dt = (this->*m_dt_function)(freq); }
+};
+
+LFO::LFO(/* args */): Oscillator(Sine, 0.f, 0.5f)
+{
+}
+
+LFO::~LFO()
+{
+}

inc/Oscillator.h

@@ -9,9 +9,7 @@ class Oscillator {
     float m_key;
     float m_volume;
     float m_phase;
-    float m_phase_dt;
     float (Oscillator::*m_osc_function)(void);
-    float (Oscillator::*m_dt_function)(float freq);
     void SineOscPhaseIncr();
     void SawOscPhaseIncr();
     float CalcSawPhaseDelta(float freq);
@@ -22,6 +20,10 @@ class Oscillator {
     float Sign(float v);
     float SineOsc();
 
+  protected:
+    float m_phase_dt;
+    float (Oscillator::*m_dt_function)(float freq);
+
   public:
     Oscillator(OscillatorType osc, float fine, float volume);
     ~Oscillator();