Emerging in the mid-'90s New York underground, Mos Def, a.k.a. Yasiin Bey, has long been one of hip-hop's most widely respected names, celebrated as much for his moral thoughtfulness as his poetics and musical smarts. Not that he's above sordid temptations, as on the respectful tribute to female form "Ms. Fat Booty". His musical instincts are never stronger than on the reflective singsong of "UMI Says", a cosmic jazz instrumental which seems to inspire an ambitious hunger in him. His poetic skills are at their peak alongside Talib Kweli on "Respiration", an atmospheric love letter to lonely New York nights.