He made listening to the transistor radio a magic moment for every teenager in love during the late '50s and early '60s. Yet Doc Pomus, one of the most influential of all songwriters in the rock era, died March 14 almost unknown to most fans of the music he helped invent. The lyricist of such early rock hits as ''Little Sister,'' ''Save the Last Dance for Me,'' ''This Magic Moment,'' and ''Teenager in Love,'' Pomus stands with Chuck Berry as one of the first songwriters to effectively adapt traditional black and Latin music to lyrical themes directly related to the lives of Levittown teens. Born Jerome Felder in 1925, Pomus created most of his biggest hits with composer Mort Shuman, although he also wrote songs with B.B. King, Dr. John, and others. Afflicted with polio in childhood, he spent much of his life in a wheelchair, and died of lung cancer in his lifelong hometown, New York City.