Hypnagogic hallucinations for me aren't in my head -- the objects (always lots of spiders) are as real as reality, but instantly disappear when I put the light on, leaving my brain trying to figure out where they went (it takes time to realise it has been tricked).

I can't really see objects in my head, but music I can play perfectly like it's an iPod. Usually just gets stuck on one track all day, though.