Simoneau was the prototypical Mozart tenor, with an unusually sweet voice, strong breath control, easy pianos and pianissimos, and graceful phrasing. His unstrained head voice also made him ideal for French lyric roles, such as Wilhelm Meister in Mignon, Nicias in Thais, and Nadir in Les Pêcheurs de Perles, operas in which he enjoyed great success as well.
He studied in Montreal with Salvator Issaurel and made his operatic debut there in 1941, as Hadji in Delibes' Lakmé. In 1949, he made his debuts in Paris, at the Opera-Comique as Vincent in Gounod's Mireille and at the Opera as Tamino in The Magic Flute. His Glyndebourne debut was in 1951 as Idamante in Mozart's Idomeneo, and he made his La Scala, Vienna Staatsoper, Salzburg, and Met debuts in Mozart roles as well. While Mozart and French operas made up his core repertoire, he also appeared in the lighter Italian roles, including Alfredo in La traviata.
He married soprano Pierrette Alarie in 1946. After their retirements, they founded the Canada Opera Piccola a touring company that specializes in nurturing young singers, in 1986. (One of Opera Piccola's alumni is tenor Richard Margison.) Though the performance version is heavily cut, his Idamante in Pritchard's first recording of Idomeneo (EMI CHS7 63685-2) is ravishing, as is his Nadir on Philips under Fournet (Philips 434 782-2).