[chokosaki]

I have a question that seems to be more complicated than it should be....

Which is correct?

"I play guitar."
or
"I play the guitar."

I assumed that both are correct depending on context.
Such as...."I play the guitar" is more definitive. I can say that if someone is asking me "do you play guitar or drums?" However, in a general statement I can say "I play guitar."

So, I want to know which is correct? I have a friend studying for his TEFL and he is curious. He says straight up and down that it can only be 'I play the guitar' and that the other is always wrong.

I'm an American btw and am more concerned with the American English part, however, if there is a difference between British English and American English, I would like to know. Thanks.