Another factor, industry sources say, is that the generation of singer-songwriters who came of age in the sixties and seventies is at a point where they’re thinking about their legacies, as well as estate planning. On December 4, Primary Wave Music Publishing announced that it had acquired a majority stake in the catalog of singer-songwriter Stevie Nicks, in a deal that The Wall Street Journal reported valued her compositions at $100 million. That deal and Dylan’s could trigger more big catalog transactions. This is a unique prize, however. Among the songwriters of the rock era, only the Beatles are as influential as Dylan, the only songwriter to win the Nobel Prize for Literature. The catalog includes more than 600 compositions, written over the course of six decades, including “Blo...