Known as “La Voz” (the voice), Hector Lavoe was for a time in the 1960s and ’70s the biggest star in the Latin music firmament. A passionate singer whose collaborations with bandleader Willie Colon were both musically innovative and highly danceable, Lavoe was also a tortured drug addict who eventually died of complications from AIDS.

Unfortunately, the film made about this charismatic performer’s life is further proof, as if any were needed, that watching self-destructive personalities self-destruct is tedious and anti-cinematic. Although it’s obvious that real-life husband-and-wife team Marc Anthony and Jennifer Lopez (playing Lavoe and his wife Puchi) are passionate about the project, and really throw themselves into their performances, El Cantante plays like two wildly different films: one a melodrama filled with endless screaming matches between husband and wife, the other a concert film in which Anthony channels Lavoe to brilliant, hip-swaying effect.

The problem here is not just that Leon Ichaso’s direction is flashy but empty, or that the screenplay is clichéd and paint-by-numbers (country boy comes to the big city, gets in with the wrong crowd and starts a long, downward spiral). El Cantante purports to be, on a certain level, a film about Puerto Rican nationalism and how the music of Lavoe, Colon and others raised the profile of a people and became an important element in their diaspora. But the way this is told is so wafer-thin, so lacking in specifics, it will ultimately resonate only for salsa fanatics or members of the Latino community. Anglo viewers new to the material will remain unenlightened.

Yet there is one big plus side to El Cantante, and that is the singing of Marc Anthony. Slim and not particularly good-looking, Anthony boasts a fabulously rich voice and a stage presence that gives new meaning to the term “sex appeal.” When he’s doing what he does best, backed by a hot band that includes original members of the Fania All-Stars and Lavoe’s own orchestra, the film soars into the heavens. Then it reverts back to another scene of domestic strife, and falls thuddingly back to earth.