Jean Gaspard Weiss was Charles Nicholas Weiss' father. I have found references to him being known as Carl, Karl, Karl Gaspard, Gaspard, Gaspar and Jean Gaspard. Goodness knows why he couldn't just choose one name and stick with it! I'm using the name Jean Gaspard because this seems to be what he was known as in France, where he came from.
Jean Gaspard Weiss was born in Mulhouse, France on 15 March 1739 to Hans Jacob and Martha (nee Schlumberger) Weiss.
Like his son Charles, Jean Gaspard was a distinguished flautist and made a living from this talent. His father Hans Jacob was a shoemaker, so although he may have been an amateur musician (pure speculation!), Jean Gaspard was apparently the first in the family to play music professionally. He privately tutored the English earl Lord Abingdon, an amateur flautist, and in the early stages of his career travelled with him. It is unknown how or where they met. In 1760 he and Lord Abingdon travelled to Rome. Lord Abingdon introduced Jean Gaspard to the artist Angelica Kauffmann, to whom he became engaged for a period.
By 1766 Jean Gaspard and Lord Abingdon were in Geneva. Lord Abingdon had returned to England by 1767, and it is possible that Jean Gaspard travelled there with him.
On 5 November 1768 Jean Gaspard appeared in a concert at the Assembly Rooms, Princess St, Bristol. On 7 May 1773 he held a benefit concert at Hickford's Room, under the direction of Messrs Bach and Abel (Johann Christian Bach and Carl Friedrich Abel). Tickets were 10s 6d each. From 1773-1778 he held a number of benefit concerts in London, often in conjunction with Antonin Kammell, and appeared in other concerts, often with Bach and Abel. Jean Gaspard was appointed as Principal Flautist to the band of King George III, possibly during this time.
During this period Jean Gaspard apparently travelled back to France and married Marie Baumgarten in Mulhouse on 20 September 1775. Almost exactly 9 months later their first child, a daughter named Charlotte Mary was born (30 June 1776). Charlotte was baptised at St Marylebone, Westminster. In around 1777 a portrait of Jean Gaspard, his wife and his daughter Charlotte was completed in Britain by an unknown artist. Further children were born and baptised in St Marylebone - Gaspar (born 12 September 1777), Mary Ann (born 6 September 1778), Sarah Elizabeth (born 19 May 1780) and Willoughby Gaspard (born 12 May 1782).
In 1784 Jean Gaspard travelled to Paris and made something of a name for himself there. He does not appear in any more concert advertising in London and it is possible he did not return to England. At some stage, having made a considerable fortune (presumably from his concerts - certainly the will of Antonin Kammell showed that he had made a reasonable amount of money from his concerts) he was lured home to Mulhouse to invest his money. However his investments went badly and he lost his fortune. He then began a fabric printing factory which was only moderately successful - a news item in World and Fashionable Advertiser on 16 October 1787 stated that "Weiss – The flute performer, who has to boast himself the master of such a scholar as Lord Abingdon – has retired from the art as a Professor – and is now more profitably occupied in the manufacture of linens in Switzerland."
During his further time in Mulhouse Jean Gaspard was active in the local intellectual and political life. He and Marie also had more children - Jean Georges (born 12 June 1785), Charles Nicholas (born 20 June 1789) and Rosine Angelique (born 12 April 1798). His wife Marie died four days after the birth of Rosine. There is every chance that there were more children in the Weiss family than this, especially considering the large gap in years between Charles and Rosine.
It would appear that Jean Gaspard may have remained in Mulhouse until his death, aged 76, on 26 May 1815, although the location of his death is unclear. No death or burial record has turned up for him in England, and there is no evidence that he returned to England. He did publish music in England in (at least) 1790 and 1801 but he surely could have done that from France. He published a relatively small number of works overall, most of which have now been lost. Later this year (17/09/2011 to 14/11/2011) the Musée Historique in Mulhouse will be holding a biographical exhibition on Jean Gaspard Weiss. I wish I could go!
P.S. If you are the person from Mulhouse who has also been researching the Weiss family, please say hello! (Post-scriptum Si vous êtes la personne de Mulhouse qui a également fait des recherches sur la famille Weiss, s'il vous plaît nous dire bonjour!/P.S. Wenn Sie die Person aus Mulhouse, der auch seit der Erforschung der Familie Weiss, bitte sagen hallo!)