Never let it be said that Sirenia aren't a revolving door when it comes to female lead singers.

First, in 2001, they employed Fabienne Gondamin, who was replaced by Henriette Bordvik later that year -- and after Bordvik's 2005 departure, Monica Pederson became her replacement in 2006.

Pederson left in 2007, and Sirenia hired Spanish vocalist Ailyn as their fourth female lead singer in 2008.

13th Floor, Sirenia's first album with Ailyn, finds them continuing to move in a more commercial direction than they favored in the early 2000s.

Sirenia's work is still goth metal, although it is goth metal with a lot of pop appeal.

Some metalheads will no doubt accuse this early-2009 release of being a sellout; anyone who called 2007's Nine Destinies and a Downfall a sellout will say the same thing about 13th Floor.

But be that as it may, melancholy offerings such as "The Seventh Summer," "Lost in Life," and "The Path to Decay" are enjoyably infectious -- and Ailyn's performances have a girlish quality that adds to the pop factor but isn't without goth qualities.

13th Floor has some death metal-ish Cookie Monster growls thanks to Morten Veland; contrasting with Ailyn's singing, those growls give the 42-minute CD a touch of "Beauty and the Beast" appeal at times.

But his growls aren't nearly as prominent as Ailyn's singing, and they don't really detract from the overall poppiness of 13th Floor.

This isn't Sirenia's most essential album or their most ambitious, but in terms of hooks and catchiness, 13th Floor is a success.