It's rare for a singer to be known as a superb vocal technician and a fine singing actor, as well as a proficient stylist. Plançon was all three of these, and while his recordings were made too early in the technology and too late in his career to give a fully accurate sense of his voice's timbre, they do capture his immense range (from top F, where most tenors have their passagio, to low D, a note at the bottom of the basso profondo range), tremendous agility, including a superb trill, and beautiful legato. A Romophone compilation shows him off in excellent vocal form, performing songs and arias.
He came from an educational line of technicians -- one of his teachers was Gilbert Duprez (who revolutionized tenor singing with his famous high C in full voice rather than falsetto and also taught Emma Albani). He made his operatic debut as Saint-Bris in Meyerbeer's Les Huguenots at the Opera de Leon in 1877, and his Paris Opera debut as Gounod's Mephistopheles (the first of many performances of that role) in 1883. There he sang in many of Meyerbeer's operas, such as L'Africaine and Le Prophète, as well as other French roles and some Italian ones. He created the roles of Don Gormas in Massenet's Le Cid and King Francois I in Saint-Saëns' Ascanio. In 1891, he joined Covent Garden for 13 seasons, and appeared in the world premiere of Stanford's Much Ado about Nothing as Friar Francis. He made his Met debut in 1893, and in later seasons sang Mephistopheles, Pere Laurent in Romeo et Juliette, Escamillo, and Saint-Bris, from the French repertoire, and also German roles such as Sarastro in the Met premiere of Die Zauberflöte and King Heinrich in Lohengrin, and Italian roles such as Ramfis in Aida. He remained at the Met until 1908.