In the midst of all his occupations he found time for music in the family circle, and in later years he used to prefer playing the viola, as he was then “in the midst of the harmony.” He would occasionally extemporise a trio or quartet on the harpsichord from a single part of some other composer’s music: if the composer happened to be present, however, he would first make sure that no possible injury would be done to his feelings.
Though kindly and generous in his criticisms of others, he would never tolerate superficiality and incompetence. He was therefore looked upon as an excellent examiner when a new organist was to be appointed to a church. He was quick-tempered, like most musicians in matters of music. It is related that on one occasion, when the organist of the Thomas Church, Görner, made a blunder, he pulled the wig off his own head, threw it at Görner, and, in a voice of thunder, cried: “You ought to be a shoemaker.”
His favourite instrument was the clavichord, on account of its power of expression: and he made his pupils chiefly practise on this. He learned to tune it and the harpsichord so quickly that it never took him more than a quarter of an hour. “And then,” says Forkel, “all the twenty-four keys were at his service: he did with them whatever he wished. He could connect the most distant keys as easily and naturally together as the nearest related, so that the listener thought he had only modulated through the next-related keys of a single scale. Of harshness in modulation he knew nothing: his chromatic changes were as soft and flowing as when he kept to the diatonic genus.”
Of his conscientiousness in examining organs and organists, Forkel ironically remarks, it was such that he gained few friends thereby. But when he found that an organ-builder had really done good work, and was out of pocket by so doing, he would use his influence to obtain further payment for the man, and in several cases succeeded.
If he happened to be away from home with his son Friedemann on a Sunday, he would make a point of attending the church service. He would criticise the organist; would tell his son what course the fugue ought to take (after hearing the subject), and would be delighted if the organist played to his satisfaction.