Letendre taught theory and practical subjects to a number of prominent musicians, including Gaston Arel, Jean Chatillon, Raymond Daveluy, Gilles Fortin, Kenneth Gilbert, Bernard and Mireille Lagacé, Lucienne L'Heureux-Arel, Michel Perrault, Gertrude Perreault-Mongeau, and Jeannine Vanier, and to his wife, Aline Letendre (b Chénier).
Aline Letendre also studied with Gabriel Cusson, and taught theory 1968-71 at the Cons de Chicoutimi and thereafter at the CMM, where she had been Cusson's assistant 1955-68. She was appointed organist at the Gesù Church in Montreal in 1957.
With the help of an MACQ bursary, and part of the time at his own expense, Letendre conducted research in musical science for many years, continuing to teach organ during that period. He left some teaching works which touched on his scientific work, and these (still unpublished in 1991) led two of his followers, Jean Chatillon and Michel Perrault, along with several others, to found in 1970 the Institut de sciences musicales Conrad Letendre, which later became Pantonal.
Letendre composed organ pieces, published in three volumes by Ostiguy (1980-2). His wife gave a recital of his works on CBC radio on the first anniversary of his death. A Conrad Letendre scholarship was awarded first in 1979 to the young Brantford, Ont, organist John Vandertuin and subsequently to Rachel Laurin. A Conrad Letendre Festival was held annually in St-Hyacinthe from 1979 to 1983.
In 1987, a concert commemorating the tenth anniversary of his death took place in the Gesù Church with the participation of Gaston Arel, Raymond Daveluy, Rachel Laurin, and Aline Letendre. For this occasion, Aline Letendre and the violinist Tara-Louise Perrault premiered Michel Perrault's Sonata in A Minor dedicated to the memory of Conrad Letendre.