Added Song and subclasses

audio/SongInstance.java

@@ -0,0 +1,35 @@
+package audio;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class SongInstance {
+
+	private String difficulty;
+	
+	private List<ObjectInstance> objects;
+	
+	public SongInstance(String difficulty)
+	{
+		this.difficulty = difficulty;
+		
+		objects = new ArrayList<ObjectInstance>();
+	}
+	
+	public void addObjectInstance(ObjectInstance obj)
+	{
+		objects.add(obj);
+	}
+
+	public List<ObjectInstance> getObjects() {
+		return objects;
+	}
+
+	public String getDifficulty() {
+		return difficulty;
+	}
+
+	public void setDifficulty(String difficulty) {
+		this.difficulty = difficulty;
+	}
+}