In 1966, Ades authored the textbook "Choral Arranging" - a standard in the field. He retired from the Waring organization in 1975, but continued to write and analyze music almost to his death.

One of his last known arrangements was for lifelong family friend and professional musician and composer Roger Rossi. Mr. Rossi remembers, "Hawley Ades and I were friends for fifty-five years. We both took piano lessons from his mother, Mary Findley Ades. I've had a warm and lasting friendship with his entire family. Naturally, upon completing my Ave Maria, I sent it to Hawley." Rossi went on to say that Ades' quickly replied, "the piece is absolutely beautiful, and I'd like to write an SATB arrangement for it." To that Rossi stated, "I was shocked he'd do that. While still mentally sharp, he was 95 years old, and half blind! He had to use a magnifying aid to see his notes while scoring. Gradually, note-by-note he plodded away until it was done. It was a chore that exemplified the man's great work ethics, congeniality, and talents all the way through to his later years. He did it for me, and I'm so proud of him. Unfortunately, he never heard his own arrangement. I'm sure he would've been thrilled like I was. The world is a better place now, because Hawley Ades was here."