function toggleGenreNode (idToToggle) {
    var nodeToToggle = document.getElementById('subgenre' + idToToggle);
    var toggleSpan = document.getElementById('toggle' + idToToggle);

    if (nodeToToggle.style.display == 'none') {
        // open the node
        nodeToToggle.style.display = 'block';
        toggleSpan.replaceChild(document.createTextNode('–'), toggleSpan.childNodes[0]);
    } else {
        // close the node
        nodeToToggle.style.display = 'none';
        toggleSpan.replaceChild(document.createTextNode('+'), toggleSpan.childNodes[0]);
    }

    return false;
}