The majority of concerts given in Vienna during Mozart’s life were private events. Many were given in the great houses of the upper nobility, most of whom kept some musicians on their staff and the richest of whom (the Esterhàzys, the Lobkowitzes and others) employed complete orchestras. More recently the practice had spread to the lesser nobility and the bourgeoisie, creating semi-public musical salons. Most of the concerts in which Mozart normally took part were of these two types; sometimes he gave one at his own lodgings:
“Dear Father! I must write in the greatest haste, for it is already half-past five and I have asked some people to come here for a little concert. Altogether I have so much to do that often I do not know whether I am on my head or my heels. […] The evening is [therefore] the only time I have for composing and of that one can never be sure, as I am often asked to perform at concerts” (M to his father, 28/12/1782)*
“Dear Father! It is impossible for me to write very much, […] as I am invited to a concert at Court Councillor Spielmann’s”(04/01/1783)
Mozart could not rely on being paid for such appearances; he might perhaps receive an honorarium, or a present such as a new snuffbox, or a free meal. He went to keep his name before the public, and perhaps to gain pupils and patrons.