As the '60s drew to a close, Blue Note spent less time than ever with adventurous music, since it didn't sell as well as soul-jazz or mainstream hard bop. So, it may seem a little strange that the label invited Andrew Hill back to record in 1968, two years after he last cut a session for the label. Hill's work for the label stands among the most challenging cerebral post-bop of the '60s, but there was another side of Hill that wasn't showcased on those records: He also had a knack for groove and melody, as indicated by his composition "The Rumproller," a hard-grooving hard-bop classic made famous by trumpeter Lee Morgan. That was the side that Blue Note wanted to showcase on Grass Roots. Hill and his band were working from the basic template of making a commercial hard-bop album, but nevertheless pushed themselves to challenging territory. Blue Note sat on the session however, and Hill went back to the studio four months later with a new group of musicians: trumpeter Lee Morgan, tenor saxophonist Booker Ervin, bassist Ron Carter, and drummer Freddie Waits. This group was every bit as adventurous as the last, but they laid down a solid groove without compromising the music. The end result may not be as bracing as Hill's earlier works, but it's a pleasure to hear him in such a genial, welcoming mood. Furthermore, the record is hardly insubstantial musically -- the songs have strong melodies, even hooks, to bring casual listeners in, but they give the musicians the freedom to find a distinctive voice in their solos. It's the best of both worlds, actually -- accessible, just like Blue Note wanted, without compromising Hill's integrity