Paul Joseph Smith was born on October 30, 1906, in Calumet, Michigan, the second of four sons to Joseph J. Smith and his wife Anna. His father worked as a clerk in a copper mining office, then sometime after 1914 moved the family to Caldwell, Idaho where he became a bank accountant. Despite this prosaic business career, Paul's father had studied violin as a young man in Minneapolis and Paris. Paul spent his later childhood growing up in south Caldwell City. According to his Disney Legends biography, Paul's father instructed his prodigy son in a variety of musical instruments, and by his teenage years Paul was conducting the high school band.
After finishing high school in the spring of 1923, Paul Smith attended the College of Idaho in Caldwell, where his father had become a professor of music in 1921. He spent two years studying there, then transferred to the Bush Conservatory of Music in Chicago in the fall of 1925. Much later in life Paul would feel there was a little too much Bach, Chopin, and other classical symphonic influences in his musical education. He was awarded a Juilliard scholarship in Music Theory, but it is not known whether he studied in New York. Two years at the conservatory were followed by a job teaching brass at nearby Elmhurst College. He also taught music at York High School in Elmhurst, Illinois, but by the Spring of 1930 he was unemployed and living back at home with his parents in Idaho. That summer Paul Smith moved to Los Angeles where he enrolled at UCLA, majoring in English. He was discouraged about a career teaching music, and had decided to switch to writing musicals.
At UCLA he had his own dance band, the Paul Smith Orchestra, which played in the big varsity shows called Campus Capers. Paul Smith told interviewer David Tietyen long afterwards how impressed he was by the technical virtuosity of an early Mickey Mouse cartoon, in which Mickey's piano playing not only matched the musical notes of the soundtrack, but also showed him pressing the correct keys on the instrument. Larry Morey, a friend of his from the Campus Capers shows, had started working at Disney and persuaded Paul to come there too.
Paul joined the Disney studio full time in 1934. Initially assigned to arranging background music for cartoon shorts, he quickly picked up the techniques for scoring animated scenes. During the next twenty-five years he would arrange and score some seventy cartoon short features. His first major assignment was working along with Leigh Harline under Frank Churchill's direction on arranging music for Snow White, for which the trio received an Oscar nomination.
Sometime during the thirties Paul Smith married, eventually having two children, a boy and a girl, by his wife. He shared the Oscar in 1940 for the score of Pinocchio with Leigh Harline and Ned Washington (The latter two gentlemen also received an Oscar for their song When You Wish Upon a Star). He would continue scoring animated feature films throughout the forties, garnering Oscar nominations for Victory Through Air Power, Saludos Amigos, Three Cabelleros, and Song of the South. For the last two films, he scored and arranged only the animated sequences.
He received another Oscar nomination in 1952 for helping score and arrange Cinderella, though as with all his film work prior to 1956 the songs in the movie were written by others. It would remain his personal favorite of all the films he worked on according to an interview he gave after retiring. Paul's adept musical characterizations of animated creatures led Walt Disney to give him a try at real live-action animals. He would score most of of the True Life Adventure films, including Beaver Valley, Nature's Half Acre, Bear Country, Secrets of Life, The Living Desert, The African Lion, and The Vanishing Prairie. Paul Smith told a later interviewer he found a special joy working with nature and animal films, though he had no pets as a child.
Walt Disney explained Paul Smith's success in the True Life films by referring to his ability to make music visual. Certainly Paul's scoring made the films more palatable to theatre audiences by imbuing the animal subjects with an emotional color. At the time this was perceived as a virtue, though some later critics would consider it an unwarranted anthropomorphism, a "Disneyification" of the natural world. Nevertheless, the films made a hefty profit for little real investment, and Paul's contribution was recognized and rewarded with his first major dramatic live-action film assignment 20,000 Leagues Under the Sea in 1954. He also received an honorary Doctor of Music degree from the College of Idaho in May 1955.