Different time signatures in different staves and midi.

[Giovanni Roversi]

First of all sorry for my bad bad english: correct me, so I can improve!
I'm using Lilypond 2.12.2.
I'm writing a piece in wich the organ and other instruments play in 4/4,
but a sort of lead synth solo is in 7/8. So, I want to write this
producing also a midi file. But, in the snippets I found, there's not
the \midi { } parameter, and if I add it doesn't work. I pasted the
\layout {...} of the snippets in my file, but doesn't work too.
How can I do what I want?
I created the structure of the score using the "New Score" function in
Frescobaldi.
Sorry for the italian names of notes: I hope you understand.
Thank you and bye bye,
   Giovanni from Italy

7\\8+4\\4.ly
Description: Text Data

7\\8+4\\4.pdf
Description: Adobe PDF document