Naval science considers the Battle of Lepanto (1571) to be the turning point from muscle to wind power but large vessels continued to use oars and sweeps as auxiliary propulsion until the advent of steam.

The chanty era began and ended entirely within the steam age. The steam powered rotary printing press had far more effect on popular culture than sails, oars or engines.

Chanties sound less like 18th century plain song or plain chant and more like 19th century popular song because... they were produced, packaged and consumed by 19th century popular culture.