That's the thing, anyone can create poetry. But only a group of people of the same taste will appreciate it. There aren't any rules, if you suck at singing, your cd will probably be dead in sales, but that doesn't make it "not music". I've seen there's people for everything in the world, and when people start saying he is not singing right it's usually about the context. If you're gonna sing opera of course you need to sing opera-like, but in general you should be able to experiment in any sense. That's how new styles are born.