Unchained at last: the soul of Bobby Hatfield (far right), the tenor half of the Righteous Brothers, the ''blue-eyed soul'' duo who, with producer Phil Spector, turned out a succession of hits in the '60s, including ''Unchained Melody,'' ''You've Lost That Lovin' Feeling,'' and ''Just Once in My Life.'' On Nov. 5, 63-year-old Hatfield died of a heart attack in Kalamazoo, Mich. In recent years, he and fellow Righteous bro Bill Medley (the pair were not siblings, just a preternaturally well-matched vocal team) had been performing on the Las Vegas circuit. In 1992, Bruce Springsteen tapped Hatfield to contribute vocals to ''I Wish I Were Blind'' on the Boss' Human Touch album. Earlier this year, the Righteous Brothers were inducted into the Rock and Roll Hall of Fame.