Bernac was well known as a teacher; among the singers who studied with him were Elly Ameling, Grace Bumbry, Mattiwilda Dobbs, Carol Neblett, Jessye Norman and Gérard Souzay.

Having no accompanist and knowing that Poulenc was in Salzburg, Bernac sent him a three-line note: "I have been asked to sing some Debussy in three days' time.

[10] The Second World War delayed their American debut until 1948;[4] The New York Times said of Bernac, "the integrity and elegance of his singing quickly won him a following among connoisseurs of art song interpretation".

[11] Poulenc wrote 90 songs for Bernac, "his style influenced by the baritone's peculiarly refined artistry", according to Grove's Dictionary of Music and Musicians.

Although Bernac avoided the operatic stage after 1936, Poulenc relied on him for technical advice on vocal matters when writing his opera Dialogues des Carmélites, and his late Gloria.

"[12] Other composers who wrote for Bernac include, from France, André Jolivet, Henri Sauguet and Jean Françaix; from Germany, Paul Hindemith; from England, Lennox Berkeley; and from the US, Samuel Barber.

Others who studied with Bernac include Elly Ameling, Grace Bumbry, Mattiwilda Dobbs, Carol Neblett and Jessye Norman.

[14] The Musical Times called him "an outstanding teacher of song interpretation – visionary, precise, tireless and loving.

The second chapter consists of technical advice on French vowel and consonant sounds and their proper vocal production.

[18][19] The original French text was published in Paris by Buchet-Chastel the following year as Francis Poulenc et ses mélodies.

With its fine literary style … it is an unselfconscious exposé of the spirit of being French, and an object lesson in how to approach any musical repertory with a high degree of rationale, but above all a warm heart".