how to transpose midi one octave ?

[Martin Tarenskeen]

Hi,

I'm sure my question is answered somewhere in the docs, but I can't find 
it:

I have a guitar score and the MIDI output should sound one octave lower 
than the written notes. I have found sections about transposing 
instruments, but not about an instrument that plays in the written key, 
but one octave down - like a guitar.

How do I handle this in Lilypond ? ( And I don't want a treble clef with 
an "8" below or an 8va basso sign in my score either)

--

Martin