There's no music.. I know that I can never sing very well without the music to accompany me. And yes, it's practise.. I find that if I sing close enough to something solid (like my computer monitor) the sound bounces off it and back into my ears better and I can hear whether I am off pitch or not... You only have to listen to a handful of really famous singers to know that they all can't sing like Celine Dion. The most obvious example of this is Bob Dylan, he has.. let's say.. a unique voice. ;)

A microphone won't make you sing better, it will just let you hear yourself (eg. through headphones) much easier and be able to much more easily hear yourself going off key etc