+\version "2.14.0"
+
+\header {
+ lsrtags = "tweaks-and-overrides"
+
+ texidoc = "
+Some grobs can be accessed @qq{laterally} from within another grob's
+callback. These are usually listed as @qq{layout objects} in the
+@qq{Internal properties} section of a grob-interface. The function
+@code{ly:grob-object} is used to access these grobs.
+
+
+Demonstrated below are some ways of accessing grobs from within a
+NoteHead callback, but the technique is not limited to NoteHeads.
+However, the NoteHead callback is particularly important, since it is
+the implicit callback used by the @code{\\tweak} command.
+
+
+The example function defined below (\"display-grobs\") is probably not
+that useful, but it demonstrates that the grobs are indeed being
+accessed.
+
+
+Example console output:
+
+
+@example
+--------------------
+#-Grob Accidental -
+#-Grob Arpeggio -
+#-Grob Stem -
+@end example
+
+
+"
+ doctitle = "Using ly:grob-object to access grobs with \\tweak"
+}
+
+#(define (notehead-get-accidental notehead)
+ ;; notehead is grob
+ (ly:grob-object notehead 'accidental-grob))
+
+#(define (notehead-get-arpeggio notehead)
+ ;; notehead is grob
+ (let ((notecolumn (notehead-get-notecolumn notehead)))
+ (ly:grob-object notecolumn 'arpeggio)))
+
+#(define (notehead-get-notecolumn notehead)
+ ;; notehead is grob
+ (ly:grob-parent notehead X))
+
+#(define (notehead-get-stem notehead)
+ ;; notehead is grob
+ (let ((notecolumn (notehead-get-notecolumn notehead)))
+ (ly:grob-object notecolumn 'stem)))
+
+#(define (display-grobs notehead)
+ ;; notehead is grob
+ (let ((accidental (notehead-get-accidental notehead))
+ (arpeggio (notehead-get-arpeggio notehead))
+ (stem (notehead-get-stem notehead)))
+ (format #t "~2&~a\n" (make-string 20 #\-))
+ (for-each
+ (lambda (x) (format #t "~a\n" x))
+ (list accidental arpeggio stem))))
+
+\relative c' {
+ %% display grobs for each note head:
+ %\override NoteHead #'before-line-breaking = #display-grobs
+ <c
+ %% or just for one:
+ \tweak #'before-line-breaking #display-grobs
+ es
+ g>1\arpeggio
+}