Javascript to edit CSS Style

I am having trouble getting my JavaScript code to change the CSS style of my article element. I have this in the opening tag for my article element:
”’

<img id="n1" onmouseover="visible('c1')" src="img/musicnote1.png" alt="Music Note">

”’
and then at the bottom of my body section I have my script tag:
”’

<script>
    function visible(a){
        document.getElementById(a).style.display = initial;
        document.getElementById('default').style.display = none;
    }
</script>

”’
I am trying to make the ‘c1’ article appear and the ‘default’ article disappear when the user hovers over the image. Neither of these actions are working