If Elmore James had never recorded his best-known tunes, the obscurer end of his output would still cement him as blues royalty. His instrumental approach—his headlong momentum, overdriven sound and boogie beat—foreshadowed the arrival of rock ‘n’ roll, which you can hear on the sizzling instrumental "Country Boogie" as much as on his biggest hits. A catalogue as full of gems as James’ is liable to have some slip through the cracks.