A label-compilation project showcasing the varied and growing talents of the rejuvenated Solesides crew, now known as Quannum, Quannum Spectrum represents the unparalleled ambition of one of underground rap’s most respected collectives. Though the critics have given DJ Shadow most of the attention, Quannum Spectrum boasts excellent productions and intricate rapping from a half-dozen important figures, including Chief Xcel and Gift of Gab (from Blackalicious), Lateef the Truth Speaker and Lyrics Born (from Latyrx), plus — for one track — guest producer El-P. Opening with the groovy Quannum/Jurassic 5 soundclash “Concentration,” Quannum Spectrum works through over a dozen wildly diverse tracks, subtly reinforcing the concept of a free-form late-night radio show (it’s occasionally broken up by spoken-word meanderings by “host” Mack B. Dog). Though “Storm Warning” and “Divine Intervention” provide a one-two punch early on, the album really never lets up; midway, an irresistible groove number (“People Like Me” by Joyo Velarde) fades into a great Lyrics Born number (“I Changed My Mind”) that plays more like blues-rock than hip-hop. It’s easily one of the most effective statements of purpose ever produced in hip-hop, much less the underground rap scene. – John Bush