Which is which?

[Sky]

Which one is correct?

1. I play the piano.

2. I play piano.

3. I play a piano.

Thanks

[Joe Carillo]

The first sentence you provided is correct: "I play the piano."

The rule in English is that the name of particular musical instruments should be preceded by the article "the." So, in the same vein as "the piano," we say:

"I play the organ."
"I play the guitar."
"I play the violin."