Science has demonstrated the health benefits of marijuana, but test results on its musical outcomes remain inconclusive. Think of the New Riders of the Purple Sage (get it?) as an uncontrolled experiment about how four decades of ganja immersion affects music that's not quite country, not quite rock and not quite hillbilly swing. Still led by founder David Nelson, NRPS sounds like the Grateful Dead (at various times, Garcia, Hart and Lesh all jammed with the band) with more twang, less songwriting vision (though the late John Dawson had the country-blues touch) and only one drummer. The band's self-titled debut isn't American Beauty, but spark up a fatty, order in a pineapple pizza and give it a spin — you'll be headed for '70s country-rock heaven.