+ // audio_column_ can be 0 when prepare has not been called. The
+ // condition is triggered when Simple_music_iterator implicitly
+ // creates a Score context, like when writing
+ //
+ // \score { { | c4 c c c } \midi { } }
+ //
+ // The same situation happens with the Score_engraver group, but it
+ // would appear not to suffer any bad side effects.
+
+ if (!audio_column_)
+ audio_column_ = new Audio_column (context ()->now_mom ());