+ (make-sequential-music
+ (append
+ (map (lambda (x) (make-grob-property-set x 'direction
+ (if (odd? n) -1 1)))
+ direction-polyphonic-grobs)
+ (list
+ (make-property-set 'graceSettings
+ ;; TODO: take this from voicedGraceSettings or similar.
+ '((Voice Stem font-size -3)
+ (Voice Flag font-size -3)
+ (Voice NoteHead font-size -3)
+ (Voice TabNoteHead font-size -4)
+ (Voice Dots font-size -3)
+ (Voice Stem length-fraction 0.8)
+ (Voice Stem no-stem-extend #t)
+ (Voice Beam beam-thickness 0.384)
+ (Voice Beam length-fraction 0.8)
+ (Voice Accidental font-size -4)
+ (Voice AccidentalCautionary font-size -4)
+ (Voice Script font-size -3)
+ (Voice Fingering font-size -8)
+ (Voice StringNumber font-size -8)))
+
+ (make-grob-property-set 'NoteColumn 'horizontal-shift (quotient n 2))
+ (make-grob-property-set 'MultiMeasureRest 'staff-position (if (odd? n) -4 4))))))
+
+(define-safe-public (make-voice-props-override n)