Mos Def strikes me as a a guy more my style, so i'll have to give him some heavier listening. You won't be disappointed. To the best of my knowledge, here's his major label release genesis: '98 - Black Star (self-titled), incredible duo album with Talib Kweli... another solo artist to check out if you don't know, but he's not rap/rock mix '99 - Black on Both Sides '04 - The New Danger '06 - True Magic '09 - The Ecstatic I haven't listened to his latest album, but I definitely can listen to any of the others regularly & in their entirety/ies. He also put out some large collaborative albums, We Are Hip-Hop (Vols. 1 & 2) in '07. I have those, don't listen to them as much, probably should more. But really for the sound you specifically described in the lead post, The New Danger is what you want for sure. Part of the reason why is i just got somewhat disenchanted with rap over the last 5-6 years or so as kinda mindless bling rap had seemed to have taken over that music form. Oh man, there's so much good stuff out there. I feel like Obi-Wan... "you've taken your first step into a larger world". I know BF.net can get your back here, danzig, & rattle off tons of great hip-hop acts beyond Mos Def & Talib Kweli. Let's see if I can come up with any more... Lupe Fiasco, The Roots, not exactly underground. M.F. Doom, Aesop Rock, Brother Ali ... honestly though I have no idea if anything I've heard of can actually still qualify as underground.