\version "2.11.43" 
\relative c' {
  % parentheses on single notes (with articulations) and inside chord
  c'4 \parenthesize c \parenthesize c-. <\parenthesize c> |
  % parenthesized articulations, rests and whole chords
  c-\parenthesize-. \parenthesize r \parenthesize <c e g>2-> |
  % parenthesizing other music expressions does nothing
  \parenthesize {c4 c-. <c e g> r} 
}