When Susan Wadsworth founded Young Concert Artists Inc. and converted a Greenwich Village loft to a concert hall for talented unknown musicians 24 years ago, she had visions of them one day performing in the Nation's Capital. Today the Young Concert Artists Series begins its sixth season in Washington with the first of four concerts. Clarinetist Daniel McKelway, 20, makes his debut here at 2:30 this afternoon at the Kennedy Center's Terrace Theater.

"Presenting series in New York and Washington is the backbone of what we do because giving young artists, not known, a chance to play in major cultural capitals is a very important step," says Wadsworth. Young Concert Artists Inc., a nonprofit organization based in New York City, received more than 400 applications from around the world last year and selected only four new musicians to add to the 16 it already sponsors. It has booked concerts in this country and abroad for its performers in the 1984-85 season and handles everything from travel arrangements to publicity.

McKelway says the organization "makes it possible to make a career as a musician much more immediate." And Wadsworth says, "We do absolutely everything we can dream up. YCA keeps artists until their careers develop where they can go on to commercial management."

The series continues in March with soprano Dawn Upshaw, violinist Chantal Juillet and pianist Jeremy Menuhin.