While our first official language is English (spoken by 99% of everyone) there is still some room for the Maori language (they are very musical!).
That said, almost all Maori music is sung in English
I don't enjoy listening to it, it isn't really my sort of music. Most of it is rap/hip-hop - typically with American underpinnings. I tend to think that it is a sad example of the declining importance of traditional Maori culture generally. They have imported the American 'Negro Gangster' stereotype into their youth; and in turn they are losing touch with their tradition, and inevitably their cultural identity.
Perhaps the music isn't the cause, it's probably a symptom of a wider cultural malaise; but it is certainly sad to see.