from here
'Bal' is Old Cornish for 'mine place', but was widely replaced, from the 18th century, with the word 'Huel' and then 'Wheal'. A bal maiden, then, means a young woman who worked at the mine. In use, probably from about 1800, it was initially used to describe the younger single women only. Eventually it was used for any female ore dresser, whatever her age or status.
'ee did the Baaz-vile scrape = he did scrape the bass viol (a large stringed instrument something like a modern double bass, often used in old church bands)

According to the Cornish dialect dictionary
Coose. Coosing.............. Chase. Hunt, Pursue
Cooze. Coozing..............ldle gossip. Wasting time
And it also apparently means a wood, but none of these meanings seem the one intended here