Tonight at Metro, a stacked bill of extreme monsters plays a sold-out show, and smack dab in the middle—between grindcore pioneers Napalm Death and Japanese noise rockers Melt-Banana—are sludge-metal masters the Melvins. Long-running and wildly prolific, they’re about to release their second LP of the year, June’s Basses Loaded, a collection where the band’s core members—singer-guitarist King Buzzo and drummer Dale Crover—collaborate with five different bass players. The cast includes bassists who’ve played in the Melvins at different points during their three-decade run, including Jared Warren from Big Business, Jeff Pinkus of the Butthole Surfers, Trevor Dunn from Mr. Bungle and Fantomas, and their newest member, Steve McDonald of Off! and Redd Kross. Crover steps away from the kit and plays bass on four tunes from Basses Loaded, and one song even features low end from Nirvana’s Krist Novoselic. Today’s 12 O’Clock Track is “Hideous Woman,” with McDonald on the four-string—this is the trio on the road right now, and they give classic Melvins ooze a proggy, dexterous edge. If you’re going to the show tonight, I envy you.