Horrorpops put out goth rockabilly.

There is a one-off album of Elvis songs done in the style of Trent Reznor called Nine Inch Elvis.

Then there's Nerdcore, which is nerds who rap. MC Frontalot, Mega Ran, MC Hawking (they used the same text to speech engine that Dr Hawking used, he was apparently amused by them), Baba Binkman, MC Lars are all examples with different interests.