Piano music is typeset in two staves connected by a brace. Printing such a staff is similar to the polyphonic example in More staves,
<< \new Staff { ... } \new Staff { ... } >>
but now this entire expression must be interpreted as a
PianoStaff
\new PianoStaff << \new Staff ... >>
Here is a small example
\new PianoStaff << \new Staff { \time 2/4 c4 c g' g } \new Staff { \clef bass c,, c' e c } >>
More information on formatting piano music is given in Piano music.
This page is for LilyPond-2.6.3 (stable-branch).