The works by which he is best known are the six sets of sonatas, with rondos and fantasies too, which he published between 1779 and 1787 in Leipzig under the title of _Sonaten für Kenner und Liebhaber_ (‘Sonatas for Connoisseurs and Amateurs’). Many of the sonatas, however, had been composed before 1779. An earlier set, dedicated to the Princess Amelia of Prussia and published in 1760, bears the interesting title, _Sechs Sonaten fürs Clavier mit veränderten Reprisen_ (‘Six Sonatas for Clavier with Varied Repeats’). This title, together with Bach’s preface to the set, shows conclusively that in repeating the sections of movements of sonatas, players added some free ornamentation of their own to the music as the composer published it. The practice seems to have been an ancient one, applied to the suite before the sonata came into being. Thus some of the _doubles_ of Couperin and Sebastian Bach may be taken as special efforts on the part of the composers to safeguard their music from the carelessness and lack of knowledge and taste of dilettanti. To what an extent such variation in repeat might go and how much it might add to the richness of the music are shown, for example, by the double of the sarabande in Sebastian Bach’s sixth English suite. Emanuel Bach’s sonatas are of very unequal merit. The sonata in F minor,[28] published in the third set for _Kenner und Liebhaber_ in 1781, but written nearly twenty years earlier, has little either of extrinsic or intrinsic beauty to recommend it. Not only does the inchoate nature of the second theme in the first movement fail to save the movement from monotony; the first theme itself is stark and devoid of life. There is a lack of smoothness, a constant hitching. The andante is not spontaneous for all its sentimentality, and the final movement is fragmentary. A sonata in A major, on the other hand, written not long after, and published in 1779, is charming throughout. The first theme in the first movement is conventional enough, but it has sparkle; and though the second theme is not very distinctly different from the first, the movement is full of variety and life. Particularly charming are the measures constituting an unusually long epilogue to the first section. The harmonies are richly colored, if not striking; and the use of the epilogue in the development section is most effective. So is the full measure pause before the cascade of sound which flows into the restatement. The andante is over-ornamented, but the harmonic groundwork is solid and interesting. The last movement suggests Scarlatti, and has the animated and varied flow which characterizes the first.