Oh, gracious. These days, hard rock is a most denigrated genre of music, is it not? With all those Mudvaynes and Slipknots besmirching the landscape, how can any self-respecting individual bang his head without feeling a wee bit peevish? Luckily, the clouds occasionally part for such honorable acts as Monday's performers. To be sure, Trent Reznor and Joshua Homme have made sterner works than their most recent efforts -- With Teeth and Lullabies to Paralyze, respectively -- but at least they can hold their heads high in the knowledge that they formulate superior big-riff metal to what is usually visited upon the lamentable mallrats of America. Nevertheless, while both auteurs are renowned for their exemplary live shows, one cannot wholly dismiss a troubling dread that, alas, these two rock institutions may be reaching their zenith. Regrettable, dear chums -- and even more reason to pay them homage while they remain in our midst.