Although the proto-black-metal band's history includes a good many peaks and valleys, Celtic Frost's influence on heavy music is undeniable. After a lengthy lull in activity and artistic direction, the Swiss band makes something of a return to form on Monotheist, an almost 70-minute slab of seething rage full of doom-and-gloom-laden riffs and near industrial-sounding drums, all led by lead guitarist/vocalist Tom Gabriel Fischer's powerful voice. Most impressive, however, is the album's conceptual cohesion. It ends with the three tracks of Triptych, including the crushing 14-and-a-half-minute marathon Synagoga Santanae and the final piece, Winter (Requiem, Chapter Three: Finale), a sombre and brooding string arrangement that's as beautiful as it is menacing. Celtic Frost demolish the Opera House Monday (September 18).