Question: The Aeolian Singers are based in the English county bordered by which county on its north?

full_context: Document 1: Leavesden, Hertfordshire: Leavesden is a residential and commercial area in Hertfordshire, England, contiguous with the northern suburbs of Watford. It lies within the M25 Motorway. On its eastern side it is bounded by the M1 Motorway. Leavesden is part of Abbots Langley civil parish and is also the name of a district council ward in Three Rivers District. Leavesden Green is an adjoining residential community which lies partly in Three Rivers and partly in the Borough of Watford.
Document 2: East of England: The East of England is one of nine official regions of England at the first level of NUTS for statistical purposes. It was created in 1994 and was adopted for statistics from 1999. It includes the ceremonial counties of Bedfordshire, Cambridgeshire, Essex, Hertfordshire, Norfolk and Suffolk. Essex has the highest population in the region.
Document 3: Vivace Youth Chorus of San Jose: The Vivace Youth Chorus of San Jose is a choral program for children from ages four to eighteen. Youth from throughout the Silicon Valley participate in six program levels. The chorus offers a well-rounded program that balances vocal training, music theory, and performances. Upper choir levels take part in choral festivals and tours. Choristers gain exposure to various musical genres, from traditional folk to classical, jazz, and contemporary. The chorus collaborates with area composers and musicians, as well as with other ensembles, including Opera San Jose and San Jose Symphonic Choir.
Document 4: Sistine Chapel Choir: The Sistine Chapel Choir, as it is generally called in English, or properly the "Coro della Cappella Musicale Pontificia" in Italian, is one of the oldest choirs in the world, having been formally active since 1471. Based in Vatican City, it normally comprises twenty men (tenors and basses) and thirty boys (sopranos and altos), the latter receiving free tuition.
Document 5: South Oxhey: South Oxhey is a suburb of Watford in the Watford Rural parish of the Three Rivers district of Hertfordshire, England. It is located in the south western corner of Hertfordshire and close to the boundary with Greater London. At the 2011 Census South Oxhey's population was included in the Northwick Ward of Three Rivers Council.
Document 6: Essex: Essex is a county in the East of England immediately north-east of London and is one of the home counties. It borders the counties of Suffolk and Cambridgeshire to the north, Hertfordshire to the west, Kent across the estuary of the River Thames to the south and London to the south-west. The county town is Chelmsford, which is the only city in the county.
Document 7: Hertfordshire: Hertfordshire ( ; often abbreviated Herts) is a county in southern England, bordered by Bedfordshire to the north, Cambridgeshire to the north-east, Essex to the east, Buckinghamshire to the west and Greater London to the south. For government statistical purposes, it is placed in the East of England region.
Document 8: Hertford Loop Line: The Hertford Line (also known colloquially as the Hertford Loop) is a branch of the East Coast Main Line, part of the Northern City Line commuter route to London for Hertford and other Hertfordshire towns and an occasional diversion route for the main line. The line is part of the Network Rail Strategic Route 8, SRS 08.03 and is classified as a London and South East Commuter line.
Document 9: Aeolian Singers: The Aeolian Singers, president Peter Skellern, musical director Stephen Jones, rehearsal pianist Anna Le Hair, was established in 1963. With about 80 members, it is Hemel Hempstead's largest mixed-voice chorus. While based in Hertfordshire, the singers also perform in major London concert halls and in other parts of Europe. In recent years they have performed in Ghent, Paris and Provence and visited Mannheim in October 2006, where they performed in two concerts together with the Konzertchor der Stadt Mannheim. They have a very wide repertoire ranging from Renaissance to contemporary music, and have given several first performances. They also have a tradition of community and youth involvement.
Document 10: University of Utah Singers: The University of Utah Singers (UU Singers) was the premier choral ensemble at the University of Utah until 2010. The ensemble was organized in 2003 by Dr. Brady R. Allred. Composed of approximately 45 voices, the ensemble performed repertoire from a wide range of musical styles and eras. In their short history, UU Singers achieved both national and international acclaim, winning the Grand Prize at the 2005 Florilège Vocal de Tours International Choir Competition in Tours, France, winning the European Grand Prix Choral Competition in Tolosa, Spain in 2006, winning first prize at the 11th International Chamber Choir Competition Marktoberdorf in 2009, participating in the 19th Festival “Choralies de Vaison-la-Romaine” in France and the 37th Abu Gosh international vocal music festival near Jerusalem. The UU Singers performed in concerts throughout England, France, Spain, the Netherlands, Italy, the Czech Republic, Hungary, Croatia, Slovenia, Austria, Germany and Israel on five international concert tours, and has appeared on French national television at the Nancy International Choir Festival.
Document 11: St George's Singers: St George's Singers is a large choral society founded in 1956 and based in Poynton, Cheshire. The choir regularly performs at venues across Manchester, with repertoire including major classical choral works alongside more unusual modern works and commissions. Its current Musical Director is Neil Taylor, and its current president is Marcus Farnsworth. Past Musical Directors include Stephen Williams. The choir also has strong links with the Royal Northern College of Music and Chetham's School of Music.
Document 12: Oratorio Society of New York: The Oratorio Society of New York is a not-for-profit membership organization that performs choral music in the oratorio style. The Society was founded in 1873 by conductor Leopold Damrosch and is the third oldest musical organization in New York City. The Society had a prominent role in the building of Carnegie Hall. Throughout its long history, it has premiered many new choral works.
Document 13: Hatfield, Hertfordshire: Hatfield is a town and civil parish in Hertfordshire, England, in the borough of Welwyn Hatfield. It had a population of 29,616 in 2001, increasing to 39,201 at the 2011 Census. The settlement is of Saxon origin. Hatfield House, the home of the Marquess of Salisbury, is the nucleus of the old town. From the 1930s when de Havilland opened a factory until the 1990s when British Aerospace closed, Hatfield was associated with aircraft design and manufacture, which employed more people than any other industry.
Document 14: Stellenbosch University Choir: Stellenbosch University Choir (Afrikaans: "Stellenbosch Universiteitskoor" ) is a Choir attached to Stellenbosch University. Founded in 1936, it is the oldest choir in South Africa. The current conductor, André van der Merwe, was appointed at the beginning of 2003. The Stellenbosch University Choir has toured overseas extensively and won critical acclaim for its performances. The choir is viewed as a leading South African choral ensemble. In October 2016, the choir celebebrated its 80th anniversary with a reunion.
Document 15: Middlesex: Middlesex ( , abbreviation: Middx) is a historic county in south-east England. It is now entirely within the wider urbanised area of London. Its area is now also mostly within the ceremonial county of Greater London, with small sections in other neighbouring ceremonial counties. It was established in the Anglo-Saxon system from the territory of the Middle Saxons, and existed as an official unit until 1965. The historic county includes land stretching north of the River Thames from 3 mi east to 17 mi west of the City of London with the rivers Colne and Lea and a ridge of hills as the other boundaries. The largely low-lying county, dominated by clay in its north and alluvium on gravel in its south, was the second smallest county by area in 1831.
ground_truth: Bedfordshire