Seven Brides for Seven Brothers is scheduled for a divorce from television . . . unless more city folk tune in. That's the word from CBS headquarters, where Nielsen numbers - spelled m-o-n-e-y - often are the only gauge for series longevity.
''Seven Brides for Seven Brothers'' (Wednesday, 8-9 p.m., check changed listings for following weeksm) has been a popular show in small-town America but a failure in the big cities. That's why this innovative singing-dancing-action show, which concentrates on old-fashioned family relationships and takes place on a ranch, is airing its last new show of the season next Wednesday and after that retires into reruns for the rest of the season.
The crucial status of the show and a need to promote it in urban America are what instigated a last-ditch publicity campaign by producers David Gerber and MGM/UA Television. That's why the star of the series, Richard Dean Anderson, has come acallin', western style.
Dressed cowboy style in jeans and workshirt, Mr. Anderson, who played the role of Jeff Webber on ABC's soap opera ''General Hospital'' for five years, is anxious to prolong the life of ''Seven Brides.'' He's tall, brown-haired, brown-eyed, and as straightforwardly honest a person as the character he plays in the struggling series.
''There's a pure aura about the show,'' he says earnestly. ''The value of the close-knit family unit is always there. And there's an honesty that's obvious in the relationship between the family members. It's probably the basis for what transpires in a lot of families throughout America, in rural and urban areas.''
Richard admits that the song-and-dance routines within the framework of the show were difficult for some audiences to accept. ''You'd walk off the ranch, scrape the mud off your boots and say, 'Hey, that reminds me of a song' and break into a dance. For lots of people that's a little hard to fathom. So, the singing and dancing have been downplayed in the last few shows and there is more of an emphasis on action-adventure.''