text:  For not only was the taste of Vienna then as now proverbially variable and flippant--not only was concert-giving an uncertain speculation and teaching an inconstant source of income--but in a man who like Mozart had from time to time strong impulses to write for the theatre it frequently happened that the order and regularity of his engagements were made to yield to the object which engrossed him; and that the profits of his time were sacrificed on the one hand without any proportionate advantage on the other