For jazz musicians, 20th-century record contracts often buried exclusivity clauses in the fine print. If a musician wanted to take a job elsewhere, he or she had to record under a pseudonym. In 1957, an alto saxophone player named Buckshot La Funke appeared on a recording released by Blue Note, but it had the unmistakable bounce of Julian &quot;Cannonball&quot; Adderley, who was signed to Mercury Records...