At birth he was given the name Louis Meuer. By the time he appeared at the St. Louis World's Fair in 1904, he had grown into a very accomplished pianist, his beautiful hands equipped with extraordinarily long and slender fingers that could span almost two octaves on the ivories. The only key he played in was F sharp. Muir attracted a lot of attention at the fair and returned to New York, where he gradually developed into a composer. His very first song, "Play That Fandango Rag," was thrust upon the public in 1909. Rehashed and reconstituted, the piece became "Play That Barbershop Chord" in 1910. Bert Williams made use of it in his stage act. Also published in 1910, an instrumental called "Chilly Billy Bee Rag" sprouted lyrics and became "When My Marie Sings Chilly Billy Bee." Muir continued to create ragtime-flavored melodies during 1910-1911, cashing in on a fad with titles like "Oh, You Bear Cat Rag," "The Matrimony Rag," and "When Ragtime Rosie Ragged the Rosary."
Success made others envious, and one day near the beginning of 1912 a journalist by the name of L. Wolfe Gilbert deliberately tried to stir up trouble in an article published by the New York Clipper. Gilbert accused Muir (and his publisher) of sacrilege for having dared to incorporate the rosary into a raggy-time song. Muir and Gilbert met in person and squared off argumentatively, almost resorting to fisticuffs until Muir challenged Gilbert to come home and write a song with him if he was so savvy. This they did, and what resulted was a piece of romantic effervescence called "Do You Feel It in the Air?" The other song they partially composed that evening was "Waiting for the Robert E. Lee," which would eventually become by far the most famous tune associated with either of them. Other Muir songs published in 1912 were "Hitchy Koo," "Dancing Dan, the Ragtime Battling Man," "Ragtime Cowboy Joe," "Ragging the Baby to Sleep," "Buck Dance Bill," "Here Comes My Daddy Now," and "Take Me to That Swanee Shore."
The year 1913 was just as productive; Muir published a rag called "Heavy on the Catsup" and the ever-productive partnership produced a string of pop songs that have since all but disappeared: "In the Heart of the Kentucky Hills," "At the Yiddish Cabaret," "He Wants Someone to Call Him Papa," "I've Been Through the Mill," "Little Rag Baby Doll," "Mammy Jinny's Jubilee," and "Oh What a Night." Muir is said to have visited London, England, where the public received him warmly as he played ragtime at the Oxford Theatre, and where he had the opportunity to work on composing a stage show with operatic composer Ruggero Leoncavallo. Muir's final year of activity was 1914. The last titles associated with his name were "Camp Meeting Band," "Buy a Bale of Cotton for Me," "I Had a Gal, I Had a Pal," and "Mootching Along." His life was interrupted by tuberculosis. He succumbed to the disease on the 3rd of December 1915. Lewis Muir had only reached his 32nd year.