That is just your pretty URL. Your actual url is something like this node/52.
So in your contextual filters, choose provide default argument and then select the content id from the URL. Views will pull in the 52 number for your referenced entity and that will filter your block accordingly.
Since you are manually creating your URLs, and idea here would be to grab the first and second element from your path. I do not recommend this. I would recommend you adding another field to reference the artist on the news basic page so you can use that value in your contextual filter. Anyway here is what you could do.
In the contextual filter, when providing a default value, use the PHP filter and add something like this to return the value of the NID of the artist.
$path = drupal_get_path_alias($_GET[‘q’]);
$path = explode(‘/’, $path);
// This path should be something like artists/picasso
// The idea here would be to get the artists node path
// and then retrieve the node id from that.
$node_artist_path = drupal_get_normal_path($path.'/'.$path);
// ^ should return something like node/33
$nid = arg(1,$node_artist_path);
This will return the value of nid from the artists main path. AGAIN I do not recommend this as its very dependent on path aliases.
Also I did not test any of this code, I may have some functions wrong and if I do let me know and I will update it, this is all from memory.