Correction Appended

MOVIES based on the lives of popular musicians constitute a durable genre in Hollywood, and also a fairly safe one. While not many of them rise to the level of greatness -- "Coal Miner's Daughter," Michael Apted's life of Loretta Lynn, comes closer than most -- there are very few that manage to be completely unwatchable, though "De-Lovely" certainly tried.

"Walk the Line," James Mangold's movie about Johnny Cash, settles down in the fat middle of the bell curve, providing, if nothing else, an excuse to go out and buy some CD's. Well cast, competently written (by Mr. Mangold and Gill Dennis) and carefully costumed, it adheres to a familiar "Behind the Music" formula, following its subject through childhood trauma, marriage and divorce, alternating off-stage melodrama with recreated performances that remind us why we should care about this guy in the first place.

Comparisons with Taylor Hackford's "Ray," which opened around this time last year, are inevitable. Both pictures place on the shoulders of their relatively young stars -- Jamie Foxx and, in this case, Joaquin Phoenix -- the burden of impersonating characters whose real voices, faces and mannerisms could hardly be better known. (For good measure, "Walk the Line" also gives us brief glimpses of actors playing Elvis Presley, Roy Orbison, Waylon Jennings and Jerry Lee Lewis.)

There are, moreover, some striking biographical similarities between Johnny Cash and Ray Charles, both of whom worked with the filmmakers telling their stories, though neither lived to see the final product. Like "Ray," "Walk the Line" tells the tale of a poor Southerner, born in the early years of the Great Depression, whose childhood was marked by the death of a beloved brother. Between the humble beginnings and the eventual immortality come events that seem almost interchangeable, more like stock situations than lived experiences. Vintage tour buses rumble down nighttime back roads. Drug habits are acquired -- heroin for Charles, prescription pills for Cash -- leading to trouble with the law and painful scenes of withdrawal. The houses and the record labels get bigger (Charles moved from Atlantic to ABC, Cash from Sun to Columbia), the groupies come and go, and the long-suffering wives and girlfriends occasionally burst into angry tears.