Bach had married in October, 1707. In 1708, while at Muehlhausen, his first considerable work, composed for the municipal elector, appeared. His election at Saxe-Weimar was undoubtedly owing to his playing before the Duke Wilhelm Ernst, and we can imagine with what pleasure the young musician, conscious of great power, looked forward to the intellectual and cultured life for which Weimar was renowned. In the course of a few years Bach was appointed orchestral and concert director to the Duke. The liberal atmosphere of Weimar, the appreciation of men whose opinion was of worth, could but stimulate the mental faculties and widen the range of thought, and there is a breadth of conception and majesty in Bach at this period unknown before. With the assiduity of genius he labored for the realization of his ideal. Palestrina, Lotti, and Caldara were laid under contribution. The master transcribed the works of these composers with his own hands, and arranged the violin concertos of Vivaldi for the harpsichord and organ. It is ever with the greatest artists. They assimulate all the forms of kindred art, yet never sacrifice their individuality. The means enabling them to express their inmost soul must be found, but their soul will alone dictate the form which its expression will assume. But Bach is approaching the close of the first period of his career. An invitation has been given him (1717) to become conductor of the orchestra at the court of Leopold of Anhalt-Koethen, a prince remarkable for his benevolence and cultured attainments. Here his duties were comparatively slight and his leisure abundant. Hitherto he had been engaged, as it were, in the temple service. At Weimar he had developed into a great tone-poet of sacred song. With refined strength and exquisite perception he had gathered up the related parts of song, weaving them into a unity of impassioned and majestic utterance. But the great poet must have a wider experience. He must enter, as it were, into the great deeps of sacred emotion in things natural; he must perceive in the universe a deeper, a more majestic beauty even than in the temple. Then he will become a great prophet among his fellows, and illumine for all time the pathway of life, giving strength to the weak, consolation to the weary, and song to the blithe and pure of heart. This is what Bach became in tone. His attention at Koethen was directed mainly to instrumental music. We have previously remarked upon the endeavors which certain German masters made to bring home to their countrymen an appreciation of instrumental music. How long the seed lay germinating in Bach's mind we know not. A new idea had taken possession of him, or, rather, he contemplated the application of the principle of his former labors in polyphony to instrumental music pure and simple. At Koethen he supplemented his labors at Weimar. At Leipsic, whither we shall presently follow him, he brought them to completion.