Here's a newspaper piece from 1953:
Singers of Commercials Branch Into Own Show
By ALINE MOSBY
United Press Hollywood Correspondent
HOLLYWOOD, May 27. — That “Four Sportsmen” quartet which parlayed a “Hmm” into fame and fortune on Jack Benny’s radio program, said today they're branching into their own show so they can really sing.
The four male crooners thank Benny hourly for giving them overnight success on his CBS program. But, they sighed, they can only give out with a cigaret commercial and “hmmm” that's a running joke on the show.
Like Phil Harris, Dennis Day and other Benny alumni, they’re taking the plunge on their own.
Two Singers
“Bob Crosby sings on the show and so does Dennis Day, so they don’t need us for regular songs,” explained Guerney Bell, Bill Days, Jay Meyer and Marty Sperzel—only not all at once.
“We’ll still stay with Benny, but we have our own transcribed radio show now so we can really sing songs.”
The hit they made as Benny’s foils have brought them a string of other sideline businesses, too.
The Sportsmen incorporated themselves and invested in a housing project, an oil well, a company in the Philippines, a helicopter and a play that flopped.
They’ve scored success on personal appearance tours, after a battle to convince booking agents they could do something besides a musical “hmmmm.” They also plan a series of television films.
“We went into these businesses together on our motto, ‘United we sing, divided we fall,’” quipped Days.
The “Hmm” on the Benny show started a joke.
“Don Wilson, the announcer, was to do the commercial and rather than make it a stereotyped thing, they decided to have a quartet do a hum. Then Benny could say, ‘For
his I pay $500?’ and faint,” said Meyer.
Backing
The Sportsmen already were singing as “backing” for such name chirpers as Ginny Sims and Dinah Shore. The unknown quartet was hired for the Benny show. They were such a hit that Benny kept them on. On one program Benny threatened to sell them to rival Fred Allen, and CBS was flooded with irate letters defending the quartet.
One member of the combination has a pitchpipe to give the quartet their cue for the “Hmmm.”
“Once we missed the note, so on the next show Benny locked us in the closet and made us say the commercial 500 times,” grinned Sperzel.