diff --git a/src/apu/dmc.rs b/src/apu/dmc.rs
index e344902..b700064 100644
--- a/src/apu/dmc.rs
+++ b/src/apu/dmc.rs
@@ -1,7 +1,24 @@
 impl super::DMC {
     pub fn new() -> Self {
         super::DMC {
-            
+            sample: 0,
         }
     }
+
+    
+    pub fn control(&mut self, value: u8) {
+        
+    }
+    
+    pub fn direct_load(&mut self, value: u8) {
+        
+    }
+    
+    pub fn sample_address(&mut self, value: u8) {
+        
+    }
+    
+    pub fn sample_length(&mut self, value: u8) {
+        
+    }
 }
\ No newline at end of file
diff --git a/src/apu/mod.rs b/src/apu/mod.rs
index 3d21862..eb5d53f 100644
--- a/src/apu/mod.rs
+++ b/src/apu/mod.rs
@@ -46,7 +46,7 @@ struct Noise {
 }
 
 struct DMC {
-
+    sample: u16,
 }
 
 impl Apu {
@@ -91,16 +91,21 @@ impl Apu {
             0x4015 => self.control(value),
             0x4016 => (),
             0x4017 => self.frame_counter(value),
+            _ => panic!("bad address written: 0x{:X}", address),
         }
     }
 
     fn mix(&self) -> f32 {
-        let square_out = self.square_table[self.square1.sample + self.square2.sample as usize];
-        let tnd_out = self.tnd_table[(3*self.triangle.sample)+(2*self.noise.sample)+self.dmc.sample as usize];
+        let square_out = self.square_table[(self.square1.sample + self.square2.sample) as usize];
+        let tnd_out = self.tnd_table[((3*self.triangle.sample)+(2*self.noise.sample) + self.dmc.sample) as usize];
         square_out + tnd_out
     }
 
-    fn frame_counter(value: u8) {
+    fn frame_counter(&mut self, value: u8) {
         
     }
+
+    fn control(&mut self, value: u8) {
+
+    }
 }
diff --git a/src/apu/noise.rs b/src/apu/noise.rs
index 93b66b3..59b4e4d 100644
--- a/src/apu/noise.rs
+++ b/src/apu/noise.rs
@@ -19,6 +19,17 @@ impl super::Noise {
         self.linear_feedback_sr >>= 1;
         self.linear_feedback_sr |= feedback << 14;
     }
+
+    pub fn envelope(&mut self, value: u8) {
+        
+    }
+
+    pub fn loop_noise(&mut self, value: u8) {
+        
+    }
+    pub fn load_length_counter(&mut self, value: u8) {
+        
+    }
 }
 
 // When the timer clocks the shift register, the following actions occur in order:
diff --git a/src/apu/square.rs b/src/apu/square.rs
index fe6fbf2..77b0572 100644
--- a/src/apu/square.rs
+++ b/src/apu/square.rs
@@ -8,6 +8,27 @@ impl super::Square {
             length_counter: 0,
             envelope: 0,
             sweep: 0,
+            sample: 0,
         }
     }
+
+    pub fn clock(&mut self) {
+
+    }
+
+    pub fn duty(&mut self, value: u8) {
+
+    }
+
+    pub fn sweep(&mut self, value: u8) {
+        
+    }
+
+    pub fn timer_low(&mut self, value: u8) {
+
+    }
+
+    pub fn timer_high(&mut self, value: u8) {
+        
+    }
 }
\ No newline at end of file
diff --git a/src/apu/triangle.rs b/src/apu/triangle.rs
index 15b50c2..202f21c 100644
--- a/src/apu/triangle.rs
+++ b/src/apu/triangle.rs
@@ -6,4 +6,16 @@ impl super::Triangle {
             linear_counter: 0,
         }
     }
+
+    pub fn timer_low(&mut self, value: u8) {
+
+    }
+
+    pub fn timer_high(&mut self, value: u8) {
+        
+    }
+
+    pub fn counter(&mut self, value: u8) {
+        
+    }
 }
\ No newline at end of file