How strategic is it for a tenor to invite comparison with Enrico Caruso, first superstar of the phonograph? If it’s “Celeste Aida” or the Flower Song from Carmen he’s wanting to sing, maybe not so much. But with his latest CD, Caruso 1873 (Sony Classical), the erratic, intermittently glorious Franco-Italian tenor Roberto Alagna has combed his precursor’s discography for a potpourri of bonbons you mostly won’t know or wouldn’t associate with a tenor. Case in point: the program launches with the philosopher Colline’s farewell to his overcoat, from the last act of La Bohème. Colline’s a bass, folks! But Caruso did record the gloomily graceful vignette, in the original key. So, why not Alagna? —M.G.