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diff --git a/src/main/java/com/jsyn/unitgen/FourWayFade.java b/src/main/java/com/jsyn/unitgen/FourWayFade.java
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+/*
+ * Copyright 1997 Phil Burk, Mobileer 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.
+ */
+
+package com.jsyn.unitgen;
+
+import com.jsyn.ports.UnitInputPort;
+import com.jsyn.ports.UnitOutputPort;
+
+/**
+ * FourWayFade unit.
+ * <P>
+ * Mix inputs 0-3 based on the value of two fade ports. You can think of the four inputs arranged
+ * clockwise as follows.
+ * </P>
+ *
+ * <PRE>
+ *      input[0] ---- input[1]
+ *        |             |
+ *        |             |
+ *        |             |
+ *      input[3] ---- input[2]
+ * </PRE>
+ *
+ * The "fade" port has two parts. Fade[0] fades between the pair of inputs (0,3) and the pair of
+ * inputs (1,2). Fade[1] fades between the pair of inputs (0,1) and the pair of inputs (3,2).
+ *
+ * <PRE>
+ *    Fade[0]    Fade[1]    Output
+ *      -1         -1       Input[3]
+ *      -1         +1       Input[0]
+ *      +1         -1       Input[2]
+ *      +1         +1       Input[1]
+ *
+ *
+ *      -----Fade[0]-----&gt;
+ *
+ *         A
+ *         |
+ *         |
+ *      Fade[1]
+ *         |
+ *         |
+ * </PRE>
+ * <P>
+ *
+ * @author (C) 1997-2009 Phil Burk, Mobileer Inc
+ */
+public class FourWayFade extends UnitGenerator {
+    public UnitInputPort input;
+    public UnitInputPort fade;
+    public UnitOutputPort output;
+
+    /* Define Unit Ports used by connect() and set(). */
+    public FourWayFade() {
+        addPort(input = new UnitInputPort(4, "Input"));
+        addPort(fade = new UnitInputPort(2, "Fade"));
+        addPort(output = new UnitOutputPort());
+    }
+
+    @Override
+    public void generate(int start, int limit) {
+        double[] inputAs = input.getValues(0);
+        double[] inputBs = input.getValues(1);
+        double[] inputCs = input.getValues(2);
+        double[] inputDs = input.getValues(3);
+        double[] fadeLRs = fade.getValues(0);
+        double[] fadeFBs = fade.getValues(1);
+        double[] outputs = output.getValues(0);
+
+        for (int i = start; i < limit; i++) {
+            // Scale and offset to 0.0 to 1.0 range.
+            double gainLR = (fadeLRs[i] * 0.5) + 0.5;
+            double temp = 1.0 - gainLR;
+            double mixFront = (inputAs[i] * temp) + (inputBs[i] * gainLR);
+            double mixBack = (inputDs[i] * temp) + (inputCs[i] * gainLR);
+
+            double gainFB = (fadeFBs[i] * 0.5) + 0.5;
+            outputs[i] = (mixBack * (1.0 - gainFB)) + (mixFront * gainFB);
+        }
+    }
+}