You can probably still classify Aesop Rock as “underground” hip-hop. Although by this point he has an established fan base far removed from anything “underground,” Aesop is still left of center, nowhere near what’s going on in “mainstream” hip-hop these days. On None Shall Pass, a lot of things that wooed early listeners remain: his unconventional voice delivering sharp, tongue-twisting rhymes over dark, hard-hitting beats. For his fourth album (not counting this year’s Nike-commissioned, one-track All Day), Aesop reflects on days gone by, but not in the carefree-ยญadolescent tone he perhaps intended. A lot of times it’s hard to follow what he’s saying โ€” not because it’s muddy, but, as on “Bring Back Pluto,” it sounds like he’s telling a story about stolen goods or something being seized. Not exactly fun and carefree, right? “Coffee,” featuring Mountain Goats principal John Darnielle, pairs the two in a bleak backdrop of stutter-step beats, tempo shifts, scratching and Darnielle’s nasally voice. Overall, Aesop’s presentation, more sick beats and grooves, is great. Knowing what he’s dissecting, well, that’s still iffy.