"Oi is a British and Australian working class slang interjection used to get someone's attention, or to express surprise or disapproval. It is also used in Singapore, with the alternate pronunciation. It is not polite, but it is not especially offensive."
haha didn't know that... okay.. now for the genre..
oo...
"Oi! is a sub-genre of punk rock originating in the United Kingdom that sought to align punk with a working-class street-level following."
okay sub-genre of skin head punk rock