/parenthesize in drummode?

[bernie arai]

i'm trying to use the /parenthesize to create ghost notes in a drumset
part using /drummode.  i don't get any error messages from lilypond,
but i don't see any parentheses in the output (just regular
noteheads).  i have a feeling that the fact that items must be
"directly connected with a music input element" to work with
/parenthesize, but i'm not sure.

am i crazy, does this work for anyone else?

\version "2.8.1"
\new DrumStaff <<
 \context DrumVoice = "1" { s1 *2 }
 \context DrumVoice = "2" { s1 *2 }
 \drummode {
   \override Score.MetronomeMark #'padding = #4.0
   \tempo 4 = 118
   \repeat volta 2 {
   <<
     { cymc8[ hho] <hhc[ sn>-> hh16 \parenthesize sn] hh8[ hho->] hhc
<hh sn>-> }
     \\
     { bd4 r4 bd8 bd r4 }
   >>
   <<
     { hh16[ \parenthesize sn hho8->] <hhc[ sn>-> hh16 \parenthesize
sn] hh[ \parenthesize sn hho8->] <hhc[ sn>-> hh] }
     \\
     { r8 bd r4 bd8 bd r8 bd }
   >>
     }
}
> >

thanks for any help,

bernie