diff --git a/stepmania/src/NoteData.cpp b/stepmania/src/NoteData.cpp
index 9fd94b828b..3ac5280684 100644
--- a/stepmania/src/NoteData.cpp
+++ b/stepmania/src/NoteData.cpp
@@ -520,4 +520,3 @@ void NoteData::SetTapNote(int track, int row, TapNote t)
 	PadTapNotes(row);
 	m_TapNotes[track][row]=t;
 }
-
diff --git a/stepmania/src/NoteData.h b/stepmania/src/NoteData.h
index 1c255fb0ab..7a05028bce 100644
--- a/stepmania/src/NoteData.h
+++ b/stepmania/src/NoteData.h
@@ -7,7 +7,7 @@
  Desc: Holds data about the notes that the player is supposed to hit.  NoteData
 	is organized by:
 	track - corresponds to different columns of notes on the screen
-	index - corresponds to subdivisions of beats
+	row/index - corresponds to subdivisions of beats
 
  Copyright (c) 2001-2002 by the person(s) listed below.  All rights reserved.
 	Chris Danford
@@ -133,6 +133,12 @@ public:
 
 	void Convert4sToHoldNotes();
 	void ConvertHoldNotesTo4s();
+
+	// True if no notes in row that aren't true in the mask
+	bool RowPassesValidMask( int row, bool bValidMask[] );
+
+	// Remove all tap notes that fail this mask
+	void EliminateNonPassingTaps( int row, bool bValidMask[] ); 
 };
 
 
diff --git a/stepmania/src/NoteDataUtil.cpp b/stepmania/src/NoteDataUtil.cpp
index 8204aafd0a..3f306a7288 100644
--- a/stepmania/src/NoteDataUtil.cpp
+++ b/stepmania/src/NoteDataUtil.cpp
@@ -823,9 +823,47 @@ void NoteDataUtil::ShiftRight( NoteData &in )
 }
 
 
-//NUM_STEPS_TYPES
+struct ValidRow
+{
+	StepsType st;
+	bool bValidMask[MAX_NOTE_TRACKS];
+};
+#define T true
+#define f false
+const ValidRow g_ValidRows[] = 
+{
+	{ STEPS_TYPE_DANCE_DOUBLE, { T,T,T,T,f,f,f,f } },
+	{ STEPS_TYPE_DANCE_DOUBLE, { f,T,T,T,T,f,f,f } },
+	{ STEPS_TYPE_DANCE_DOUBLE, { f,f,f,T,T,T,T,f } },
+	{ STEPS_TYPE_DANCE_DOUBLE, { f,f,f,f,T,T,T,T } },
+};
 
 void NoteDataUtil::FixImpossibleRows( NoteData &in, StepsType st )
 {
-	
+	for( int i=0; i<ARRAYSIZE(g_ValidRows); i++ )
+	{
+		const ValidRow vr = g_ValidRows[i];
+		if( vr.st != st )
+			continue;	// skip
+
+		for( int r=0; r<=in.GetLastRow(); r++ )
+			if( !NoteDataUtil::RowPassesValidMask(in,r,vr.bValidMask) )	// failed mask
+				NoteDataUtil::EliminateNonPassingTaps(in,r,vr.bValidMask);
+	}
+}
+
+bool NoteDataUtil::RowPassesValidMask( NoteData &in, int row, const bool bValidMask[] )
+{
+	for( int t=0; t<in.GetNumTracks(); t++ )
+		if( !bValidMask[t] && in.GetTapNote(t,row) != TAP_EMPTY )
+			return false;
+
+	return true;
+}
+
+void NoteDataUtil::EliminateNonPassingTaps( NoteData &in, int row, const bool bValidMask[] )
+{
+	for( int t=0; t<in.GetNumTracks(); t++ )
+		if( !bValidMask[t] && in.GetTapNote(t,row) != TAP_EMPTY )
+			in.SetTapNote(t,row,TAP_EMPTY);
 }
diff --git a/stepmania/src/NoteDataUtil.h b/stepmania/src/NoteDataUtil.h
index b2f988292a..c02d14071f 100644
--- a/stepmania/src/NoteDataUtil.h
+++ b/stepmania/src/NoteDataUtil.h
@@ -64,6 +64,12 @@ namespace NoteDataUtil
 	inline void SnapToNearestNoteType( NoteData &in, NoteType nt, float fBeginBeat, float fEndBeat ) { SnapToNearestNoteType( in, nt, (NoteType)-1, fBeginBeat, fEndBeat ); }
 
 	void FixImpossibleRows( NoteData &in, StepsType st );
+
+	// True if no notes in row that aren't true in the mask
+	bool RowPassesValidMask( NoteData &in, int row, const bool bValidMask[] );
+
+	// Remove all tap notes that fail this mask
+	void EliminateNonPassingTaps( NoteData &in, int row, const bool bValidMask[] ); 
 };
 
 #endif