Jim Jacobs (born October 7, 1942) is an American composer, lyricist, and writer for the theatre. He is known for writing the book, lyrics and music, with Warren Casey, for the stage and film musical Grease. Jacobs was born on October 7, 1942 in Chicago, Illinois to Harold, a factory foreman, and Norma (Mathison) Jacobs. Jacobs attended Taft High School, during which time he played guitar and sang with a band called DDT & the Dynamiters. When he was 11, his idol was Bill Haley, but when he was fourteen it was Elvis Presley. He also cites Buddy Holly, Little Richard, and Jerry Lee Lewis as influences. When he was a teenager, he would imitate playing a guitar with a broomstick. He eventually convinced his parents to pay for guitar lessons. After four lessons, he quit and decided to buy a guitar book and teach himself. From this, his found a simple chord structure: C, A minor, F, G7—this would later be Those Magic Changes featured in Grease. In 1963, he became involved with a local theatre group that included Warren Casey, The Chicago Playwrights Center (at that time it was called Hull House Playwrights Center).