The compilers of Time-Life Music's series The Heart of Rock 'n' Roll had a challenge in assembling an entry for 1956, the earliest year for a volume so far. The series is devoted to the soft side of rock & roll, and while the transitional year of 1956 boasted many ballad hits, they were mainly performed by traditional pop singers, not rockers. Still, the year's biggest stars on the pop singles chart -- Elvis Presley, Pat Boone, and the Platters -- all had rock & roll credentials of one sort or another, and all found time for softer recordings. (Presley's recordings, previously unheard in the series, seem to have become available for licensing in the wake of RCA Victor Records' outright purchase of the Presley masters from the singer's estate.) Even though artists are usually only heard once per disc in the series, Presley and the Platters have two selections each here. But other compromises had to be made as well. The series usually focuses on big pop hits, but it has been necessary to go unusually far down the chart for selections this time and even to fudge the calendar a little. The Heartbeats' "A Thousand Miles Away" only got to number 53 in the Billboard pop chart, and it didn't do that until January 1957; Fats Domino's "Blueberry Hill" and Pat Boone's "Don't Forbid Me" also reached their chart peaks in early 1957. And then there are several tracks that were not pop hits at all, making their mark instead on the R&B charts. The Clovers' "Devil or Angel" (covered for a pop hit by Bobby Vee in 1960), Jesse Belvin's "Goodnight My Love" (simultaneously a pop hit for the McGuire Sisters), and the Dells' "Oh What a Nite" (which made the pop charts for them in a new version in 1969) all made the Top Ten of the R&B chart while not crossing over to the pop chart. But despite these adjustments, the collection gives a good sense of the more romantic, slow-tempo style of rock & roll that was already emerging in 1956. When Presley, the fire-breathing rocker of "Hound Dog" fame, crooned his way through "Love Me Tender," the final track here, he vastly increased his already burgeoning popularity and expanded the scope of rock & roll.