Available again SME reveals their free jazz roots with only hints of what was to come. "Pure pleasure is the way one might react to this glorious recording, which lays the foundation for Spontaneous Music Ensemble's more radical works to come. In part a product of its time, these tracks are much more in the vein of free jazz than the abstract free improvisational style that came to characterize the group. On Challenge, the lineage can easily be traced directly to the innovations of George Russell and Ornette Coleman, as the horns focus on short, catchy riffs that segue to tight, focused solos. Kenny Wheeler's playing is a big surprise, with thrilling, crisp spurts that point in a different direction than the some of the more staid roads he later pursued. Paul Rutherford articulates cleanly, seemingly indebted to a somewhat conservative post-bop aesthetic which he generally abandoned in later years, at least with SME. Trevor Watts' footprints are all over, as he not only appears on each of the ten tracks, but he also is credited with three tunes and he solos vigorously and highly effectively throughout. The final "Distant Little Soul" was recorded more than a year after the others, and it features a quartet with a young Evan Parker and Watts on saxes. Parker is surprisingly (at least in retrospect) tentative, playing second fiddle to his more confident colleague, who performs impressively on both piccolo and alto sax. These seminal recordings stand the test of time; they are of considerable historical value, to be sure, but just as importantly, they sound fresh and exhilarating decades later."-Steve Loewy, All Music