\header {

texidoc = "with \\applycontext, \\properties can be modified
procedurally. Applications include: checking bar numbers, smart
octavation. "

}

\score { \notes \relative c'' {
    c1 c1

    %% todo: should put something interesting in the .tex output.
    
    \applycontext
	#(lambda (tr)
	 (format #t "\nWe were called in barnumber ~a.\n"
	  (ly:get-context-property tr 'currentBarNumber)))
    c1 c1
}}
