Surviving accounts of the youth of Giulio Regondi present a Dickensian tale. Born in Geneva (or perhaps Genoa) in 1822 to an unnamed German mother who may have died at his birth, Giulio was raised by an Italian father (some say step-father or foster father) who was himself a talented guitarist, composer, and baritone. Young Regondi exhibited prodigious talents on the guitar; in Paris, in the age of such masters as Sor, Carulli, Carcassi and Molino, Regondi, usually performing in duo with his father, enraptured critics while still no more than seven or eight years old. The Spanish virtuoso Fernando Sor (1778-1839) dedicated his Fantaisie "Souvenir d'Amitiè," Op. 46 (1831) to the young Regondi and may have also written for him a Grand Duet (now lost), evidence of a relationship which implies mutual respect and suggests tantalisingly that Sor may even have played some rÙle in the young man's development. The Regondis, father and son, arrived in London in 1831 and achieved critical and financial success there, touring throughout the British Isles. Then, one day in about 1835, the father handed the child a 5 note and absconded with the rest of their money, said to have been several thousand pounds sterling.

Young Giulio somehow survived this trauma, and, with the help of friends and foster parents, became a resident of London and continued to earn a living as a performer. On one occasion, he performed in duo with another child prodigy, Catherine Josepha Pelzer, who became the doyenne of the Victorian guitar world under her married name, Mrs Sidney Pratten. In 1836 he shared a concert with the Viennese pianist Moscheles and the famous soprano Maria Malibran. Several years earlier Regondi had also taken up the newly invented concertina and quickly developed a phenomenal technique on this instrument, further evidence of his extraordinary musical talents. On the concertina Regondi performed difficult works composed for violin and other instruments, and composed virtuoso works of his own, including a concerto; the concertina's rising popularity seems to have owed a great deal to the young man's contributions. Regondi toured the continent with the cellist Joseph Lidel, performing on both guitar and concertina; once in 1841 he performed in duo with Clara Wieck Schumann in the Gewandhaus in Leipzig. There were other concert tours, but Regondi lived most of the rest of his life in England. A member of the Victorian musical establishment, he performed several times a year in London and occasionally Liverpool, and enjoyed the patronage of, among others, Sir Charles Wheatstone, the inventor of the concertina. Regondi was reputed to have a kind and gentle nature; in later life, by one account, he was contacted by the "father" who had deserted him years earlier; he readily agreed to take in the destitute old man and to care for him in his old age.