The Greek classical elements -- air, earth, fire, water -- have always made appearances in the music of Isis. The quintet's epic, time-stretching explorations often start with droney ambience and shift into dirty, sludge-packed guitar dirges, then erupt with the incandescent fury of a certain unpronounceable volcano in Iceland, and finally simmer down into an effects-wettened ebb that drifts away like a distant night tide.
But Isis fans will soon experience a new elemental sensation -- the soundless vacuum of space -- as the band has announced this tour to be its last: "Isis has done everything we wanted to do, said everything we wanted to say," the group recently decreed in an official statement. "It is time to bring it to a close." That's sad news for adventurous rock fans. Isis consistently ranked among the most progressive bands around, pushing against the boundaries of brimstone art-metal and cosmic post-hardcore like restless demigods looking for some universal exit sign.
It's the sort of music that usually attracts a cult following, and Isis was no exception. To those devoted fans, the band offers this farewell: "We are hoping that these final live rituals can help us bring a close to the life of this band in a celebratory and reverent way, and also provide us with a chance to say goodbye to many of those that have supported us over the years." Consider that your personal invitation to their retirement party.
Isis shares the stage with Tombs and Jakob tonight at Great American Music Hall. (9 p.m., $17)