Bobby Darin was a pop multiple choice test all by himself.

Among the questions raised during the extraordinary career of the singer, who was inducted into the Rock and Roll Hall of Fame in 1990:

* Was he the most versatile pop star of his generation?

* Or simply the most ambitious?

* Or, perhaps, just the most misunderstood?

All three questions come to mind--along with answers--when you listen to this excellent four-disc survey of Darin's remarkably varied career.

We are accustomed in pop to seeing superior artists go through various golden eras in their careers, as with Elvis Presley's '50s and late-'60s Memphis periods or Frank Sinatra's various triumphs on the Columbia, Capitol and Reprise record labels.

However, Darin was perhaps unique in that his golden periods each involved different musical styles--from the early rock ("Early in the Morning") to adult pop ("Mack the Knife") to R&B ("The Right Time") to country ("You're the Reason I'm Living") to folk ("If I Were a Carpenter") and beyond.

This shifting musical focus caused many pop observers over the years to discount Darin's achievements and musical vision, arguing that he was merely chasing after commercial advantage.

But that reasoning ignores the high quality of Darin's work in each field and the fact that his shifts were often counter to conventional commercial wisdom. It also overlooks his own personal drive.

Born Walden Robert Cassotto in the Bronx in 1936, Darin was haunted much of his life by fear that a congenital heart defect would prevent him from reaching the age of 30. (He died during surgery in 1973 to repair a faulty heart valve.)

The fear made him obsessed with cramming decades into a few years. "I want to be the biggest thing in show business by the time I'm 25," he once told a reporter--an attitude that caused many observers and co-workers to label him arrogant and brash. But few could deny Darin's talent.

Though he also had several acting credits (including an Oscar nomination for his supporting role in the 1963 comedy-drama "Captain Newman, M.D."), Darin's legacy was his music.

The singer, who also wrote some of his material, was 22 when he scored his first hit, a novelty for Atlantic's Atco label titled "Splish Splash" that had one-hit wonder written all over it.