How does Patrick O'Brian use imagery in The Thirteen-gun Salute?

Imagery:

John Foley, the Shelmerston fiddler, skipped on to the capstan-head; at his first notes the men at the bars stepped out, and after the first turns that brought on the strain, three deep voices and one clear tenor sang
Yeo heave ho, round the capstan go,
Heave men with a will
Tramp and tramp it still
The anchor must be weighed, the anchor must be weighed
Joined by all in a roaring
Yeo heave ho
Yeo heave ho
Five times repeated before the three struck it again
Yeo heave ho, raise her from below
Heave men with a will
Tramp and tramp it still
The anchor's off the ground, the anchor's off the ground