The "Great Gavioli Organ," designated as GV21, was constructed in 1902 as a 112-keyless model and later converted to an 89-key configuration in the post-1920s era. Often referred to as "Silcock's Gavioli" or "ex-Woolls Bros/Arthur Mills," this mechanical organ was produced by the esteemed French manufacturer Gavioli et Cie. It is one of nine "giant" models delivered to England in the early 20th century and was originally commissioned by James Crichton for his traveling cinematography shows known as "Bioscope." Alongside the White Brothers' Mammoth Gavioli Fair Organ (GV26), it remains one of the last surviving 112-keyless Gavioli organs, albeit in a modified form. The instrument operated pneumatically, powered by a 3½ hp motor that supplied compressed air through valves to the pipes, all coordinated by an 89-key keyboard that played from a perforated cardboard roll.

At the turn of the 20th century, such monumental mechanical organs were highly sought after by British showmen and fairground operators. They served as multifunctional machines that met the diverse musical needs of traveling shows or street fairs while functioning as striking visual attractions. Following the introduction of the "Electric Bioscope Cinematograph Moving Picture Show" to Great Britain from continental Europe in 1901, competition intensified as showmen vied to captivate audiences with increasingly impressive displays of moving images. Crichton's "Bioscope No. 1" (1902/03) and "Bioscope No. 2" (1908), both featuring the grand Gavioli, were on the road alongside other notable productions, including Sydney White's "Coliseum Bioscope" in South Wales and John A. Proctor's "Royal Bioscope" in Nottinghamshire. During this period, Gavioli & Co., officially known as Société Des Anciens Établissements Gavioli, was the foremost manufacturer of fairground organs worldwide, fulfilling numerous orders for their innovative 110-key and 112-keyless mechanical organs from their branches in London and Manchester.

However, the prominence of "mammoth" Gavioli organs in the UK was short-lived. Within a decade, traveling cinema shows became outdated with the rise of permanent movie theaters, while phonographs and other compact auto-reproduction devices emerged as superior technology, rendering large mechanical organs less viable. For instance, Crichton's "Great" Gavioli stood approximately 5.4 × 3 meters and weighed around 4 tons, necessitating a skilled technician for maintenance. By the early 1920s, many owners repurposed their Gavioli organs as central features for steam-powered roundabouts, carousels, and gallopers, often downsizing them to a more manageable 98-key or 89-key format.

After 1912, James Crichton sold his "Great Gavioli" to Harry Hall, who operated roundabouts and joyrides in the East Midlands. Hall utilized the organ on a scenic railway through his company, Hall & Proctor, in partnership with John Albert Proctor of "Proctor Funfairs." Eventually, the organ changed hands to John Studt, who used it on a switchback ride, and later to P. Phillips. In 1935, the organ's next owner, Steven Hadfield, chose to retain only the Gavioli's decorated façade, transferring the actual musical instrument to the Woolls Brothers, a well-known firm based in Hastings, East Sussex, since at least the early 1930s. They installed the organ on the former Hall & Proctor switchback. According to the Fairground Association of Great Britain's "A Century of Tobers" newsletter (Vol 1, No. 2, January 1978), the organ was refurbished and resized to a 110-key scale, although this contradicts most sources, which assert it was converted to an 89-key format. Reportedly, the ride was taken out of service by 1937, leading to the organ being placed in storage.

In 1958, Arthur Frederick Mills (1914–1991) from Rushden, Northamptonshire, acquired the 89-key Gavioli for preservation. A respected entrepreneur and civil servant, Mills was also known for his extensive collection of antique steam engines and fairground equipment. In the early 1960s, he co-founded the Fair Organ Preservation Society. Mills entrusted the restoration and ongoing maintenance of the Gavioli to the esteemed organ builder Victor Henry Chiappa (1900–1993) of Chiappa Ltd. in London. The Great Gavioli was featured in several critically acclaimed LP recordings, including one in 1961 on City of London, another in 1970 on Marble Arch, and a third in 1972 on Alshire. According to the FAGB's "Century of Tobers" article, the organ underwent an authentic restoration around 1978 by George Flynn (d. 1981) from Durham County, after which it was acquired by the Silcock family.