Percy Hilder Miles was born in 1878 in Crayford to parents George Miles (a local builder) and Fanny Hood (of Bexley Heath). The family moved to Erith in 1880, living in a large new end-terrace house on the corner of Queen’s Road and Avenue Road the entire time. His middle name of Hilder hails from an old East Sussex surname belonging to his maternal grandmother, Jane Hilder, who married into the Hood family. The Hoods were local bakers and musicians and it is likely that Percy’s uncle Frederick William Hood, gave him his first violin lessons.

Miles’ earliest compositions date from when he was eight years old and when he was thirteen, he performed the Beethoven violin concerto at St. James’ Hall Piccadilly, with the Principal of the Royal Academy of Music, Alexander Mackenzie, conducting. Two years later, in June 1893, he entered the RAM where his teachers included Walter Battison Haynes (1859-1900) and the Austrian violinist Hans Wessely (1862-1926).

In 1895 he encountered Lionel Tertis who at the time was also a violin pupil of Wessely. Miles suggested to Tertis that he switch from violin to viola in order for them to play string quartets together. Due to a lack of suitable viola staff at the Academy, Tertis taught himself. Three weeks later they performed to McKenzie, who encouraged Tertis to stick at it.

Miles' name appears several times in The Musical Times in the late 1890s performing works of others and his own also. According to a brief biography in one of these articles in 1899, he won the first Sauret prize in 1897, the Hine Exhibition composition prize in 1893, the Walter MacFarren Scholarship in 1896 (awarded 8 January 1896) and the Charles Lucas Medal in mid summer 1898, as well as the Mendelssohn Scholarship in 1899. In 1896 he received a silver medal presented annually to the most distinguished student at the Royal Academy of Music, the Royal College of Music, or the Guildhall School of Music, in rotation, the recipient nominated by the principal or director of the school from the Worshipful Company of Musicians.

He was made a sub-professor in 1899 and in 1903, upon his return from Mendelssohn Scholarship studies in Vienna, Berlin, Karlsruhe, Paris and Milan, became a full professor of Harmony and Counterpoint. Among his students was Rebecca Clarke who studied there from 1903 to 1905. Her father removed her from the RAM when Miles proposed marriage after a lesson in 1905. She enrolled at the Royal College of Music instead where she studied composition with Charles Villiers Stanford who also encouraged her to change to the viola, taking some lessons from Tertis.

In 1906 Miles became an overseas examiner for the Associated Board of the Royal Schools of Music. This lead to long periods of travel across the British Empire, including Australia. According to his obituary he went around the world no fewer than six times, sometimes visiting his brothers in Canada and relatives in Jamaica and Australia. One of his cousins was the famous Australian water colourist J J Hilder.

In 1909 he purchased a Stradivarius violin made in 1720, known as the "General Kyd”. He bequeathed this to Rebecca Clarke in his Will of 1912.

He was reluctant to have his works published although a handful were; his biggest success came in 1920 when his String Sextet, (alongside works by Stanford and Holst) was selected from 64 entries for publication by Stainer & Bell and won the Carnegie Trust Award, a competition open to all the Empire.

In 1922 Miles went blind in one eye and also caught pneumonia which took his life in April of that year. According to his catalogue he left over 160 works, (mainly chamber music) half of which his mother sent to his brothers in Canada after his death. Over 100 manuscripts survive with his great nephew William Stantan Miles. Around 40 survive in the RAM Archive. Others are now deemed lost. He never married and lies buried with his parents in Erith cemetery.