Live from New York: children's radio mixes interviews, records, call-ins.

It's 5 o'clock in New York City, and ''Small Things Considered'' is on the air. Broadcasting from a 1940s-vintage studio space on the 25th floor of the Municipal Building, host Kathy O'Connell of public radio station WNYC announces the evening lineup: a folk-music segment with Minstrel Bob, an interview with futurist Arnold Brown, and a report about student science fairs in town.

Billed as a ''radio news magazine'' for children, ''Small Things Considered'' is pioneering an innovative approach to programming for young listeners. According to WNYC, this new show, which airs from 5 to 8 p.m. Monday through Friday and 6 to 8 p.m. Saturday, is the only regularly scheduled live children's radio show in the country.

''A lot of people over the past few years have been trying children's programming,'' says producer Keith Talbot. Unlike other shows for children, which are based on story-time, semidocumentary, or prerecorded formats, ''Small Things Considered'' takes the disc-jockey approach with records, live interviews , and call-ins from listeners.

On this evening, about 5:20, after the opening music from ''Oliver'' and the old-time favorite ''On Top of Spaghetti,'' Minstrel Bob entertains his listeners with animal and bird songs. Children call in with questions about his guitar and how he learned to be a musician.

At 6:05, the show moves into a futurist segment focused on the question, ''What is the world going to be like in 20 years?'' Again children are invited to call in with their ideas after listening to comments by futurist Arnold Brown. Music from ''Star Wars'' and ''E. T. and Me'' rounds out the segment.

Later in the show, Ms. O'Connell plays requests for records (Michael Jackson is the unchallenged favorite) and banters with children who call in during ''Joke Time'' to tell their favorite jokes and riddles.

''Small Things Considered,'' which began in January, is solely station-supported. Despite its shoestring budget, the show has prompted an enthusiastic response from both parents and children.

''Parents like the idea of getting children away from television,'' says show director Larry Orfaly.

Mr. Talbot believes part of the appeal comes from broadcasting live and inviting listener participation. ''The kids have a chance to shape the show,'' he says.

As soon as show time approaches, the phones light up with calls from listeners who want to share a joke, request a song, talk about family or friends , or just chat about their day.

The program is geared for ages 6 to 12, but the station has heard from children as young as 3 and as old as 16 during the call-in segments.

''We find if we do something for nine-year-olds, the younger brother and sister want to listen along. It gives them a chance to interpret the topic of the hour at their own level,'' says Mr. Talbot.

Typically, each show is divided into three hour-long segments devoted to subjects such as conservation, endangered species, recycling, historic preservation, computers, religious customs, sports, and school news.

Topics are treated in a variety of ways. A segment usually includes an interview with an expert, related music, and a call-in period when children can ask questions or offer opinions on the subject. The combination makes for a fast-paced show while exploring the three topics in some depth.

During one show the station asked children to call in with responses to the question, ''What book would you take with you to a desert island?'' During the week of a citywide math test, program hosts talked with teachers about how to prepare for the test, asked children to offer their own advice, and after the test asked students how they felt about it.

The program has featured guest stars such as Mayor Koch, country-singer Tom Paxton, Mr. Rogers, and clowns from the Ringling Bros. and Barnum & Bailey Circus. Show hosts have interviewed representatives from the Museum of Natural History, the Landmark Preservation Commission, and the Bronx Zoo.

As the program evolves, the staff is considering a child guest host once a week or once a month, live tapings at city events for children, and call-ins allowing children to ask teachers questions about homework. New studios, due for completion in July, will increase production capabilities.

Whatever elements are added to the show, children's participation will continue to be emphasized.

''More than anything else kids just want to have someone listen to them with some respect and seriousness,'' says Mr. Talbot. ''In the final analysis that may be one of the most impressive things about the show.''