Gallop's new-found job lasted only a short time, as the client decided to re-hire the announcer he had grown tired of. Gallop then made a decision to quit the investment banking business based on the economic conditions of the time; there appeared to be more investment consultants than clients in need of their services. His brief previous announcing experience was enough to earn him a spot at WEEI. Gallop worked for the station for ten months before moving to New York with his friend Ed Herlihy to do network announcing.
Having failed the NBC network announcer audition on his first try, Gallop was extremely eager to be hired by the other major network at the time, CBS, as he did not want to return to Boston. When he got the job, Gallop was told his starting salary would be $45 per week. He then expressed concern that it wasn't a "round" figure. When asked to explain, Gallop swallowed hard and said he believed $50 was a "round" sum, getting his first raise before actually starting with the network.
Gallop soon established a career as a radio announcer on CBS and later with NBC; he was described as "the only announcer who sounds like he's wearing spats." He was heard on soap operas such as Amanda of Honeymoon Hill, Hilltop House, When a Girl Marries and Stella Dallas, as well as the Columbia Workshop and New York Philharmonic broadcasts. The soap operas Gallop served as the announcer for were all part of the vast radio realm of Frank and Anne Hummert, who were responsible for writing and producing at least 125 radio shows. Gallop also did some announcing for the radio show Gangbusters, was the announcer forOrson Welles's The Mercury Theatre on the Air, as well as The Prudential Family Hour. In addition to being the announcer for the radio show, The Doctor Fights, Gallop also had a dramatic role for the program's first year in 1944.
In 1945, Gallop received an unexpected call from a radio listener of Stella Dallas. The caller indicated he or she was a regular listener of the program with a question which had often come to mind: "I listen to Stella Dallas every day, purely for sport's sake, of course, and there's one thing I'd like to know. (Caller then paused) How the heck do you stand it?" Unfortunately, there is no record of Gallop's response to his caller.
As the announcer on radio's The Milton Berle Show, he was a comic foil for Berle. Addressing the star of the show as "Berle", Gallop, who was known on the show as "Mr. Gallop, sir", would deliver a series of pointed one-liners. The "voice from the clouds" concept originated with writer Goodman Ace on the Berle radio show, but was never fully developed until Gallop became Perry Como's television announcer and Ace began writing for Como. Despite a friendship between Gallop and Berle, the working conditions on the radio show were such that Gallop quit after every broadcast. Gallop was also a "Communicator" for the NBC Radio show Monitor on Sunday afternoons from 1955 – 1960.