While The Byrds’ eponymous boxed set proves how deep the band’s mine of great music went, this primer delivers what’s promised when it comes to essentials. The terrain they covered is astonishing, too. While the Bob Dylan–penned hit “Mr. Tambourine Man” and Gene Clark’s original “I’ll Feel a Whole Lot Better” minted their folk-rock formula of jangling guitars and close vocal harmonies, later cuts see them rush headlong towards psychedelic glories like “Eight Miles High” and the crystalline country rock of “Chestnut Mare”.