add .sc file

Author: Nathan Ho

BoringMixer.sc

@@ -0,0 +1,13 @@
+BoringMixer : UGen {
+    *ar { |left, right|
+        ^this.multiNew('audio', left, right);
+    }
+    checkInputs {
+        [0, 1].do { |i|
+            (inputs[i].rate != 'audio').if {
+                ^"input % is not audio rate".format(i).throw;
+            };
+        };
+        ^this.checkValidInputs;
+    }
+}