Try this:
$listMapper
->addIdentifier('title')
->addIdentifier('artist')
->add('createDate')
->add('changeDate')
->add('missing', null, array('editable' => true))
->add('_action', 'actions', array(
'actions' => array(
'view' => array(),
'edit' => array(),
'delete' => array()
)
))
;
Notice the array('editable' => true). For booleans this works, I'm not sure for other fields.