On Contours, his second Blue Note album, tenor saxophonist Sam Rivers fully embraced the avant-garde, but presented his music in a way that wouldn't be upsetting or confusing to hard bop loyalists. Rivers leads a quintet featuring trumpeter Freddie Hubbard, pianist Herbie Hancock, bassist Ron Carter, and drummer Joe Chambers through a set of originals that walk a fine line between probing, contemplative post-bop and densely dissonant avant-jazz. Each musician is able to play the extremes equally well while remaining sensitive to the compositional subtleties. Rarely is Contours anything less than enthralling, and it remains one of the high watermarks of the mid-'60s avant-garde movement.