--- /dev/null
+\version "2.11.49"
+\header {
+ lsrtags = "simultaneous-notes,tweaks-and-overrides"
+ texidoc = "
+If notes from two voices with stems in the same direction are
+placed at the same position, and both voices have no shift or the
+same shift specified, the error message \"warning: ignoring too
+many clashing note columns\" will appear when compiling the
+LilyPond file. This message can be suppressed by setting the
+@code{'ignore-collision} property of the @code{NoteColumn} object
+to @code{#t}.
+"
+ doctitle = "Suppressing warnings for clashing note columns"
+}
+
+ignore = \once \override NoteColumn #'ignore-collision = ##t
+
+\relative c' <<
+ { \oneVoice \stemDown f2\glissando \stemNeutral a } \\
+ { \oneVoice \ignore c2\glissando \ignore d, }
+>>