Odd output

[Marco Correia]

Hi,

I just started using lilypond, so it is very possible that I'm making some 
mistake.

When compiling this example:

\include "english.ly"
{
\clef treble
\time 4/4
<<
 { fs'4 } 
 \\ 
 { f'4 } 
>>
}

I see two notes on fs (occupying the same position but with stems up and 
down). There is no indication that f is there.

Is this supposed to/ how do I fix it? 

Thanks!
Marco

-- 
Marco Correia <address@hidden>

-- 
--
Marco Correia