Are these sentences correct:
1-John was violent, as he was rude.
2-He played the piano, as he did the guitar.
3-He was an amateur football-player, as he was an amateur painter.
Yes. No comma.
No. Only the second sentence might work, since both are playing something.
You expect some similarity with the use of "as" like this. "As" indicates either in the same fashion or some causality. "He carries a hard hat as he works in a refinery." "She makes wonderful pies as she learned baking from her mother."
And being a painter has nothing to do with being a football player.
Thanks a lot Dave.
Doesn't the comma in the sentences excludes the possiblity of their being about similarity in manner.
I played football as you did.=I played football like you.
I played football, as you did./as did you.=You played football and I did too.
But then again, the clause after the comma might have been added as an afterthought, in which case, it would be a manner clause and would be about similarity in manner.
1-John was violent, as he was rude.
2-He played the piano, as he did the guitar.
3-He was an amateur football-player, as he was an amateur painter.
There's probably going to be some ambiguity no matter how you write these - comma or not. For manner, you don't use a comma.
1. is correct is you mean that John is both violent and rude.
2. with the comma means he played both the piano and the guitar. Similarly with three.
If you want a manner clause, you'd need something like:
4. John was as violent as he was rude. (No comma)
5. He played the piano as he did the guitar - badly. (No comma)
6. He was a football-player as he was a painter - amateur at both. (No comma)
Dave's "He carries a hard hat as he works in a refinery" (or a sentence like it) could also mean manner rather than 'because':
"He carries a hard hat as he works in a refinery - lazily."
"She cooked pies as her mother taught her - without enough salt."