What does this phrase mean: "the times they are a-changin"

[Carbonarius]

Hello everybody

I'd like to know what the a- in the song "the times they are a-changin'" means. Actually, I've seen that form in many american songs. Could anybody explain it to me?

By the way, in this particular song there's something else I don't understand: why does it say "they"? It isn't necessary, as we already have the subject (the times).

Thanks

[Mosteque]

Hi Karlos
For me it's an americanism. I can hear it in many songs and have come across it reading american books.
I was a-thinkin'
I was a-comin'
same as i was thinking
I was coming
Pls Alan correct me if i'm wrong
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obsequium amicos, veritas odium parit

[Mosteque]

a couple of quotations from The Grapes of Wrath by John Steinbeck:

"Where ya s'pose Connie was a-goin'?"
"Goin' to take a crap, I guess"

"Guess we better git, then" Tom said. "Where you a-goin'?"
"Why, up north, like I said."

"Well, he ain't no good," Pa insisted. "All the time a-sayin' what he's a-gonna do. Never........"

"..... We'd come up a-fightin', an' I jus' can't afford to be took in an' mugged......."

"Over there," said Ma. " Come on, ROsasharn. We're a-goin'."

a piece from Nick Cave's poem:

The light in our window is fading
The candle gutters on the ledge
Well now sorrow, it comes a-stealing
And I'll cry, girl, but I'll come a-running
Straight to you
For I am captured
Straight to you
For I am captured
Once again

ok i'm tired
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obsequium amicos, veritas odium parit

[Carbonarius]

Thank you for your reply, Mihal, you're ready to help as always. But my question is: does it make any difference to say "Where ya s'pose Connie was goin'?" instead of "Where ya s'pose Connie was a-goin'?"

By the way, it seems that "The Grapes of Wrath" is a good book for learning American colloquial English.

[Mosteque]

as to your question, the difference is probably as distinct as this between i'm going to and i'm gonna
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