“THE UNKNOWN PUCCINI.” Placido Domingo, tenor (with baritone Justino Diaz in “Vexilla”), Julius Rudel, piano/organ.

CBS Records Masterworks MK 44981 (compact disc). These 15 (“Terra e Mare” is sung in two versions) rare and lovely songs find Domingo in his most relaxed good voice. The tessitura, gratefully low most of the time, enables him to lavish his burnished sound and expert projection of the texts on the charming music. Five of the songs are recorded here for the first time. Opera buffs will delight in hearing what was to become “Donna non vidi mai” (“Manon Lescaut”) in “Mentia L’Avviso,” as well as the “Boheme” quartet in “Sole e Amore.” One oddity is the “Vexilla” which contains jolting quotes from Mascagni’s “Cavalleria,” unexplained in the otherwise excellent notes. The only blemish on the recording is the woolly, strained bass of Diaz in the duet. Rudel affords expert accompaniments.