Paul Johnson’s appealingly brief biography of Mozart looks like being a lot of fun.  Here is a bit from near the beginning (pp. 9-11):

Mozart’s musical progress began in 1759, at age three, when he began to remember themes and pick out chords.  The next year he was taught brief pieces on the clavier and reproduced them correctly.  In 1761 he began to compose pieces, which his father wrote down.  It was essential to his father’s belief in his miracle-genius that his son should be displayed “to the glory of God,” as he put it.  In 1757, when Mozart was two, Leopold had been appointed court composer by the prince-archbishop, and as a senior musician, had opportunities to show off his son.  But in Salzburg they were limited, so in 1762, when Mozart was six, he took him to Munich, capital of Bavaria, to play before the elector.  Nannerl went with them, as a co-prodigy, and by now a very accomplished one.  But as a child of eleven, she did not raise much of a stir.  Mozart did, and was feted at many fashionable gatherings.

Next they went to Vienna, capital of Austria and of the German- speaking musical world, in so far as it had one. Maria Theresa, the empress, who had survived the attempt by Frederick the Great of Prussia to destroy her and was now a formidable woman, received them graciously but, though a robust Catholic, showed no signs of treating Mozart as a personified miracle.  She was not unmusical.  On the contrary, she was gifted, a fine singer, and had been educated musically by her vice Kapellmeister, Antonio Caldera. But her advisers were strongly against spending much on music.  Under Emperor Charles VI, her father, and his Hofkapellmeister, Johann Joseph Fux, there had been 134 musicians in the imperial chapel.  Under Maria Theresa, the number fell to 20.

Hence, the empress received the Mozarts, but that was all.  Her daughter, Marie Antoinette, picked Wolfgang up when he fell on the slippery parquet flooring.  Her mother listened patiently when he played a difficult piece by Georg Christoph Wagenseil.  When he jumped up onto her lap and kissed her, she made no complaint. Leopold got a bag of Maria Theresa thalers; the children, presents of court dresses, in which they were painted (not too well).  But no job was offered. Later, when her son did offer some kind of job, she objected, in a devastating letter: “You ask me about taking the young Salzburger into your service.  I do not know why, believing you have no need for a composer or useless people.  If, however, it would give you pleasure, I would not hinder you. What I say is so that you do not burden yourself with unproductive people, and even give titles to people of that sort.  If in your service, this debases the service when such people go around the world like beggars. Furthermore he has a large family.”

The last point is curious as Leopold did not have a large family.  Otherwise the letter gives a telling glimpse of how a sovereign saw music on the eve of its greatest age in history.  Musicians were exactly in the same position as other household servants - cooks, chambermaids, coachmen, and sentries.  They existed for the comfort and well-being of their masters and mistresses.  The idea that you took on a composer or performer simply because he was outstanding, when you already had a full complement of household musicians, was absurd.  And of course performing music for money, outside palace or church employment, was mendicancy.  There was plenty of it, of course.  The trade was overcrowded.  Groups played at street corners for coppers.  In London there were “German Bands.” There were also Italian street musicians, who played “Savoyards,” what we would call hurdy-gurdies, or barrel organs. All this was begging, and beggars usually had, or came from, large families: hence the empress’s error.

In short the only respectable way a musician could earn his living was in salaried employment at a court, a wealthy nobleman’s house, or a cathedral or major church.  Leopold had such a job, but it was at a low level and miserably paid.  To rise higher - at a court like Vienna or the elector’s in Munich - required interest. That was a key eighteenth-century word, usually to do with family connections.  When George Washington distinguished himself in colonial service during the Seven Years’ War, when Mozart was an infant, he aspired to rise in the British regular Army or its Indian offshoot.  But he had no interest at the Horse Guards (War Office) or the East India Company in London.  So he went on to become a revolutionary leader, and first president of the United States.  When Napoleon was a young teenager in Corsica, he greatly admired the Royal Navy ships that anchored in its harbors.  But he had no influence in the London Admiralty, and so a commission in the Royal Navy was out of his reach.  He went on to become emperor of France and conquer half of Europe.  Thus history is made.  In Mozart’s world, to become a court painter, architect, or musician required interest, and his father had none.  Fortunately in his case, he could go on “begging” by composing and performing.