function mopen() {
    if (isOpen == 0) {
    dropDown.style.visibility = 'visible';
    isOpen = 1;
    // add an event listener that closes the menu if the document is clicked
    // document.addEventListener("click", mclose, false);
    }
    else {
    isOpen = 0;
    dropDown.style.visibility = 'hidden';
    document.removeEventListener("click", mclose, false);
    }
}

// this function should've been used if the document is clicked anywhere else than on 'Tracks'
function mclose() {
    if (isOpen == 1) {
    isOpen = 0;
    dropDown.style.visibility = 'hidden';
    document.removeEventListener("click", mclose, false);
    }
}