no, I don't think Wakin's cantonese could be in any manner 'unathentic'... born in Hongkong, his first language is Cantonese rather than anything else.. ,,even he might be off from Hongkong for years... i firmly believe his cantonese still remains as perfect as ever... just like cantonese world wide, their language never deteriated....
it is unlikely that a person could forget his mother tongue.... and actually Wakin did not actually leave hongkong, his career is very much based in the region where cantonese presence is prevailent... and that was why he to produce some cantonese albums which are wonderful renditions of his style...
