Boiling down a great artist's "essentials" is always tricky, especially when that artist is Plácido Domingo, the most recorded tenor in history and one of the most versatile. Sensibly, the two discs zoom in on the split sides of Domingo's artistry: opera on the one hand, popular crossovers on the other. The lighter music shows off Domingo's charismatic vocal personality and his elegant style: The zarzuela (Spanish operetta) excerpts are particularly charming, as are the graceful songs of Cuban composer Ernesto Lecuona. The Man of La Mancha numbers are great fun, and Domingo's refined sentimentality even adds an appealing touch to the unlikely pairing with John Denver. But the classical half of this set is full of gems, too, mostly recorded in the 1970s and '80s, at the heart of Domingo's very long vocal prime. Two duets with soprano Renata Scotto, from Madama Butterfly and Adriana Lecouvreur, are real highlights: They capture the tenor fully in character and showcase his dramatic powers. For sheer virtuosity, there's the rousing "Di quella pira," from Verdi's Il Trovatore to conclude the first disc, and superb, too, are the big tenor arias from obscure operas like Mascagni's Iris and Massenet's Le Cid. Even if these "essentials" don't include the tenor's signature role -- Verdi's Otello -- or his more recent forays into Wagner, the collection offers not only a one-stop summary of Domingo, but also provides inspiration to begin exploring his extraordinary career.