Ordering by multiple columns

Can someone give me advice please.

I’m trying to get items on a page to list in order of time, so the correct output should be:

21:20 , 19:45 , 18:05 , 17:40 , 17:00

but what I’m getting is:

21:20 , 19:45 , 18:05 , 17:00 , 17:40

hours and mins are in separate columns on the db and the code looks like this:

$friday_query = new WP_Query(array(
            'post_type' => 'band',
            'meta_query' => array(
                array('key' => 'stage_name', 'value' => $post->ID, 'compare' => 'LIKE'),
                array('key' => 'stage_day', 'value' => 'friday', 'compare' => 'LIKE'),
                array('key' => 'stage_hours', 'value' => '', 'compare' => '!='),
                array('key' => 'stage_mins', 'value' => '', 'compare' => '!=')
            ),
            'meta_key' => 'stage_hours',
            'order' => 'DESC',
            'orderby' => 'meta_value'
        ));

How the hell do I make it work? I’ve tried: ‘orderby’ => ‘stage_hours stage_mins’ ? Because in my head that should work. But it doesn’t :/

Cheers,

D