The judgment of connoisseurs on Mozart's technical treatment of the violin tends to show that the difficulties even in solo parts are comparatively small, but that an acquaintance with the idiosyncrasies of the instrument, which could only be gained violin in hand, is always apparent; all is made as smooth and easy as possible for the performer, at the same time that effects of striking originality are produced. Our idea of Mozart as a violin-player will gain in interest by a knowledge of his judgment on other violinists. As a child, he had become acquainted at Mayence with the violinist Esser, of whom the father writes later from Salzburg (December 7, 1780): "Esser is a merry old simpleton; but he plays (when he is in earnest) with a firm and remarkable execution, and has a finer adagio touch than is the case with most allegro players. But when he is in a joking mood he plays on the G string alone with the greatest ease, and plays pieces with a lead pencil on the strings wonderfully correctly and quickly.[53] He plays the viola d'amour charmingly.[54] But what struck me as particularly childish was his whistling of a recitative and aria equal to any singer, with all the expression, flourishes, shakes, &c., in a truly marvellous manner, accompanying himself on the violin _pizzicato_ At the same time he laments that, like the rest of them, he cannot play without grimaces and absurdities." On this point, little Wolfgang, unimpressed by Esser's tricks and _tours de force_, had said that he played well, but made too much of it, and would do better to stick to what was written. {INSTRUMENTAL MUSIC.} (322) Of Ign. Frànzl (b. 1730), whom he heard at Mannheim, he wrote to his father (November 22, 1777): "I have had the pleasure of hearing Herr Frànzl play a concerto on the violin. I was extremely pleased. You know that I am no great lover of difficulties. He plays difficult passages so that one does not know that they are difficult, and thinks one can imitate him; which is true art. He has also a good round tone, every note is correct and clear; he has a charming _staccato_ in one bow up as well as down, and I never heard such a double shake before. In a word he is, in my opinion, no juggler, but a very good substantial violinist."