On October 18 they arrived at Milan, and set vigorously to work on the completion of the opera. The subject chosen was "Mitridate, Re di Ponto," opera seria in three acts, versified by Vittorio Amadeo Cigna-Santi of Turin, where it had already been produced in 1767 with the music of the kapellmeister Quirico Gasparini. It was first necessary to finish the recitatives begun in Bologna, and Wolfgang worked so hard at them that he excused himself to his mother for not writing: "His fingers ached so from writing recitatives." Every air in the opera was written after consultation with the singers, male and female, as to what was best suited to their voice and style. By studying the taste of the vocalists and so engaging their zeal, the composer found the best security for the favourable reception of his work. If he were not fortunate enough to please his singers, either the whole must be rewritten to suit them, or he must be prepared to hear his music fall flat before the audience, if indeed something quite different were not substituted by the performer. When the composer possessed true talent and judgment, this co-operation was less detrimental to the work than if it had been left altogether to the discretion of the performers; nevertheless, the danger of undignified subjection to their caprices was considerable. Wolfgang strove to extricate himself, as best he might, from the difficulties and intrigues which hindered his work. These were the more vexatious, as the singers arrived in Milan so late as to give him little time for composition. His father was careful not to allow him to overtax his strength, and especially insisted on his not working immediately after eating, unless under the pressure of great necessity; they usually went for a walk first. The mental strain of so important a task had a sobering effect on the boy's spirits, and he repeatedly enjoins his mother and sister to pray for the success of the opera, "so that we may all live happily {THE ITALIAN TOUR.} (130) together again." Leopold begs his friends in Salzburg to be charitable enough to write them cheerful, jocular letters, to distract Wolfgang's mind, There was, of course, the usual petty spite of the "Virtuosen canaille" to combat; they were not likely to leave unmolested a kapellmeister at once "a youth and a foreigner"; but the father shrank from no difficulties which could be overcome by "presence of mind and good sense," and declared they would gnaw through them all, "as the Hanswurst did through the Dreckberg."