There seems to be a bug in lilypond

[Shaun Zhang]

Hi
I am trying to add more than one title in the \score block, and I am trying to 
do it in conjunction with pianostaff, but it seems that the title appears to 
be exactly the same above the score when I compiled it to PDF and opened it, 
while in the code it was different titles for each block.
What I wanted was different titles in each block in the PDF version as well, 
using GrandStaff or PianoStaff in the code.
PS: if this is not a bug, how do I program it like this?
Regards
Shaun Zhang