viola fora de moda

Help me please! I understand every word, but the main idea escapes me. What's wrong with the blind man? Fora De Moda = "out of tune" or "out of fashion"?

http://www.youtube.com/watch?v=H0rUMLnYr38

Moda de viola
De um cego infeliz
Podre na raiz, ah, ah
Vivo sem futuro
Num lugar escuro
E o diabo diz, ah, ah
Disso eu me encarrego
Moda de viola
Não dá luz a cego, ah, ah

Here is my awkward translation:
"Tuning of the lute of a blind man is bad:
"I live with no future(says the lute?) at a gloomy place"
And the devil says:
"Aha, i must always keep the lute out of tune.
So that the blind man couldn't have seen the light"
Any corrections? )))

Very difficult translation. It's not easy to understant the meaninig hidden by the verses " E o diabo diz, ah, ah
Disso eu me encarrego". Anyway here is my attempt :

Out of fashion viol

Song played on a viol
By an unfortunate blind man
A decaying man since the birth

I live without hope
surrounded by darkness
The devil gloats over : Ah ah
And says : I am the responsible (for his misfortune)
Song played on a viol
Can not make the blind see