Here he continued his studies under Hertel, in all branches of music, but especially in accompaniment, at that time a difficult art, as the accompanist had only the figured bass to guide him.

The Seven Years' War put an end to Frederick’s flute-playing, and as Fasch received his salary (300 thalers) in paper, worth only a fifth part of its nominal value— a misfortune in which he anticipated Beethoven—he was compelled to maintain himself by giving lessons.

After the Battle of Torgau, the King granted him an addition of 100 thalers to his salary, but the increase covered the direction of the opera, which was put into his hands from 1774 to 1776.

After the War of the Bavarian Succession Frederick gave up his practice, and Fasch was free to follow his natural inclination for church music.

In 1783, excited by a 16-part Mass of Benevoli's, which Reichardt had brought from Italy, he wrote one for the same number of voices, which, however, proved too difficult for the court-singers.

In the summer of 1790, as he himself tells us, he began choral-meetings in the summer-house of Geheimrath Milow, which resulted in the Singakademie, an institution which under his pupil and successor Zelter became very popular and exercised an important influence on musical taste in Berlin for many years.

On the first occasion, June 21, he heard a chorale, the three first numbers of Fasch's mass, and several movements from his 119th Psalm, and he himself extemporized on one of the subjects of the latter.

The receipts amounted to 1200 thalers, an extraordinary sum in those days, and were applied to founding a Fund for the perpetual maintenance of a poor family.

Of his oratorio Giuseppe riconosciuto, performed in 1774, one terzetto alone remains, Fasch having destroyed the rest, together with several other works composed before the 16-part mass.