Creating harmonized lines

[Tim McNamara]

Is LilyPond capable of generating harmonized lines of notes?  For  
example, say I have:

\key g \major
\melody { c8 d8 e8 fis8 g1 }

for one instrument and I want a second instrument to play a  
harmonized line a third up from that (e.g., { e8 fis8 g8 a8 b1 } ),  
is there a command for LilyPond to do this?  Using "\transpose c e"   
would apply a major third interval to all the notes, resulting in the  
harmony line not being within the key of G.

I can of course just do this by hand, but I was looking for the  
automagical way if it exists.  I have not been able to find anything  
in the documentation, the mailing list archives (other than a  
discussion about how \transpose does not do diatonic transposition)  
or the snippet repository that would point to this capability.  Maybe  
I should just stop being lazy...

Tim