We play it. I don't know about the recording, but I start the tune in C on the A string and the band joins me one measure in. We took it as straight as possible (minus the keyboard) so it's probably in C on the original cut.
Makes it an easy:
C-C-A-C-A-G
C-A-G
C-A-G-A
(repeat)
Then it moves up one string, same pattern....
The turnaround is on the G and D, with the little runs that Duck did which are mportant to the feeling.