RewriteCond %{HTTP_HOST} ^([a-z]+)?-music\.blackplanet\.com$ [NC]
RewriteRule . - [E:host_prefix=%1]
RewriteRule ^/([-_a-zA-Z0-9]+)/?$ http://%{ENV:host_prefix}.blackplanet.com/music/view/artist.html?page_url=$1 [R]
RewriteRule ^/?$ http://%{ENV:host_prefix}.blackplanet.com/music/ [R]