Like the great American filmmaker William Castle, the Melvins have learned that a gimmick is a big help in getting folks to pay attention to what you're doing.

The grunge pioneers have a long, rich tradition of creatively rearranging their membership, and for a band obsessed with a thick and heavy low end, they've taken the logical step and made an album with a rotating lineup of bass players.

Basses Loaded feature six different bassists scattered among its 12 tracks, including Steven McDonald (of Redd Kross and OFF!), Jeff Pinkus (from the Butthole Surfers and Honky), Trevor Dunn (Mr.

Bungle and Fantômas), Jared Warren (from Big Business), and Krist Novoselic (formerly of Sweet 75, Eyes Adrift, and some band from Aberdeen).

The Melvins' longtime drummer Dale Crover even gets into the act, handling the four-strings on four numbers.

Since each bassist seems to bring a bit of his own personality to the performances, this means the album as a whole doesn't always cohere as strongly as you might hope, though the Melvins' twin trademarks of thundering heaviness and snarky wit are audible.

Steven McDonald, the guy with the best-documented pop sensibility of this project, is the one who brings in a Beatles cover, though "I Want to Tell You" ends up referencing "Helter Skelter" once they're done with it.

(McDonald also shows off his love for Black Sabbath on "War Pussy.") Trevor Dunn's busy upright bass lines lend a coda of jazz and prog rock to "Planet Distructo"'s metallic assault.

And Crover seems to be the go-to guy when the Melvins just want to be silly on covers of "Take Me Out to the Ball Game" and "Shaving Cream" (beware, unlike on Benny Bell's famous recording, these men have no truck with shaving cream), though Novoselic's appearance on "Maybe I Am Amused" is goofy in a truly ambitious manner.

Buzz Osborne's trademark guitar style, clever but bludgeoning, gives Basses Loaded its greatest stylistic through-line, and Dale Crover's drumming is outstanding throughout.

But most of the time, Basses Loaded is more interesting in concept than it is satisfying in execution, though the best moments suggest that future full-length collaborations with McDonald or Dunn would be worth exploring.