By Loraine Alterman, Free Press Teen Writer

One upon a time folk singers looked at electric guitars and top 40 radio in horror. Then several years back the big hero of the folk world, Bob Dylan, shocked the purists by plugging into the electric current and getting his records played on top 40 stations.

The barriers between folk and rock began to crumble. Other folk singers started recording with electric guitars and checking to see if their records made the "hot 100" charts.

Tom Rush, 25, is a popular folk singer who has released a couple of single records aimed for the top 40 charts. The first was "Who Do You Love" and the latest is "The Urge for Going" written by Detroiter Joni Mitchell.

Tom stopped in Detroit recently to talk about this new single which uses electric guitar and bass.

"If you're going to play and play for people I think you want to play for as many people as possible," Tom says in explanation of putting out a single not strictly in the folk bag.

About the screams of dismay that surrounded Dylan's departure from pure folk Tom says, "I don't think there should have been such disapproval. Music is music. But with him it was a sudden transition. . . .Whereas I always sang the early rock 'n' roll of the 50's, kind of tongue in cheek, in my act. So no one was really amazed by it."

Tom played around Boston while he was still at Harvard. After he graduated in 1964 he started performing at various folk clubs and in concert around the country. He's played for enthusiastic crowds at the Chess Mate here three times and that's where he got acquainted with Joni Mitchell.

Tom first recorded "Urge" for one of his albums last February, but it was left out of the album. Then WEZ in Boston got a tape of the song which they played and listeners started calling the station and writing Elektra Records, the company Tom records for, demanding it be put on record. So Tom re-recorded it for single release.

"Joni was born in Canada," Tom explains, "and the song is about the coming of winter which in this part of the country is pretty dramatic. It has a powerful meaning as an event. . . .It's a good song that a lot of people should hear. I think it would mean a lot of things to a lot of people."

In the pop field Tom singles out groups like the Beatles, the Stones, and the Spoonful as producing good music. "They come up with ideas that are interesting and surprising to me. They go into chord changes or melody lines that are interesting both to my ears and head as a musician."

On the other hand, he hears a lot of "slop" on the radio now too. "This stuff is completely predictable from beginning to end. All of the ideas there have been used 100 times before. Nothing is happening. There's no imagination or creativity. The only creativity is to design a record calculated to sell."

Tom's only message whether he's singing a Chuck Berry number or a folk song is to say, "Here's a good song ... I enjoy singing. I really do honestly enjoy singing songs for people because I think the songs are good."

One thing worries Tom and that's "When kids tell me 'My parents don't like folk music but they like your records.' I never could figure out what it did mean."