Here’s one good reason why you shouldn’t use Wikipedia as a reliable source for any kind of research:
In the Wikipedia entry for “Melody,” someone obviously added their own take on “what melody does.” I’m sure it will be changed soon, but how many others will visit the entry before it will? Because of this, no one should ever use Wikipedia entries as sources for research. It can be a good jumping off point, but it should never be cited in academic papers at all. Yet people still do it.