William Parsons (c.1747-1817) was a composer and musician who held the position of Master of the King's Music from 1786 to1817. One of his duties (within George III's household) was as tutor to the royal children, including Princesses Sophia, Augusta Sophia, Elizabeth and Mary. In recognition of his service he was knighted in 1795 and became the first British musician to be given such an honour. He resided at Somerset Street, Portman Square with his wife Lady Parsons (née Charlotte Sophia Worgan), whom he married in 1778.

His collection of letters, principally from the Princesses to himself and Lady Parsons, are full of fascinating insights into the musical tastes and events held by the Royal Family at this time, including a performance of Acis and Galatea at Frogmore in December 1802, and musical instruments for George III. Interestingly, the letters are also full of gossip regarding the Cheveley sisters (the daughters of Louisa Cheveley, the Princesses' nurse). In addition, the collection also demonstrates the affection in which Parsons and his family were held by the Royal Family; for example, they send congratulations on his daughter’s marriage, while the King and Queen invited both Sir William and Lady Parsons to stay with them at Frogmore after the wedding celebrations in 1803.