McLellan was also a talented chess player, writing a chess column for the Post and covering international chess matches. At the beginning of his career at the Post, he also wrote for the paper's Book World section and covered White House parties and society events for the Style section.

The Post describes McLellan as a "gentle, inquisitive and compassionate man," qualities which sometimes spurred others to label his reviews too positive. He was also modest, saying "I've never attended a concert without reminding myself that at least one person in that room knows more about that music than I do."

Slash-and-burn critiques weren't his style. Instead, in a 2001 interview in Washingtonian magazine, he compared his role to that of a gardener: "The critic notices what needs to be watered, pruned and fertilized. At the end of his time, the garden should reflect the values he embodied."

However, McLellan's reviews weren't always enthusiastically received, according to his niece, Ann McLellan Lardas. She told Playbillarts about her uncle's scrap book, in which he kept "hate mail" from those who disagreed with his critiques. She also recalls that when he interviewed Blackstone the Magician he refused a soft drink from the publicist for ethical reasons. He was also diligent, turning down an invitation to the White House Christmas Party because he had a Japanese lesson and wanted to be ready for the National Orchestra's historic tour the following summer.

McLellan was born in Quincy, Massachusetts. He received his undergraduate and masters degrees in French from Boston College in 1951 and 1953, respectively. Plans to be a professor of French literature were abandoned when he discovered a talent for journalism.

Before joining the Post as an assistant editor of Book World in 1972, he worked as a freelance reviewer; a columnist and reporter for the Pilot, a Boston-based Catholic newspaper; and as foreign news editor for Religion News Service in New York.