"I don't know anything about music. In my line, you don't have to."
-- Elvis Presley
What does "In my line" mean? What does this quote mean?
Here line is short for line of work, or profession, what one does for a living.
The quote appears to be ironic or a joke. Who knows, without further context.
He was referring to music theory. It meant you do not have to know about music theory in order to compose music. You do not even need to know it in order to be able to play music. "Line" here does not mean "line of work", but rather "line of thinking", with "of thinking" being understood: In my line [of thinking], you don't have to [know anything about music].
How true it is this quote I know very well! I too know absolutely nothing about music, yet I lately began to write songs and everybody seems to like them! Of course it is not easy to become another Elvis, but music is natural to everybody and everyone can be a songwriter with no previous music knowledge.