Oh dear, y'all are sadly lacking in info on old J.S.
The Baroque period of music began well before J.S. Bach, at least one generation before his birth in 1685. It was already coming to an end in his lifetime. By the latter part of his life, he was already somewhat out of date and when he died in 1750, the Baroque era died with him, as he was by then the only major practitioner of the Baroque polyphonic style. (So did his music until resurrected 70-odd years later mostly through the efforts of Felix Mendelssohn.) Sadly, his musician sons had little respect for the old boy's style, preferring the new Italian style then coming into vogue, which was the forerunner of the Classical style of Mozart, Haydn, etc. They used to refer to him behind his back as "the old wig", referring to the old-fashioned full bottomed wigs which the old boy wore (they wore the newer smaller style which were worn in the latter part of the 18th century).
20 children it was, 7 by his first wife, Barbara. Poor woman seems to have worn out early and suddenly. He was away on a trip with his employer and came back to learn she was dead and had been buried the preceding week. Two of his sons by this wife, Wilhelm Friedemann and Carl Philip Emmanuel were well known musicians and composers in their time. He remarried in less than 2 years, since in those days a professional man with 7 children needed a wife. His second, Anna Magdalena, was made of tougher material and bore him 13 children. One of his youngest sons by her was Johann Christian Bach, also a well-known and successful musician in his day and apparently J.S.' favorite, since in his will he left Christian two valuable harpsichords, one a pedal model (he was a teenager when his father died). Christian went to Italy to study, converted to Catholicism (no doubt causing his staunchly Lutheran father to twirl in his grave) and then went to London, where he settled, enjoying the favor of the royal court lately deprived of Handel.
Besides being the great master of the organ, J.S. Bach was also a master of the harpsichord, also known as the cembalo, or in the German of the time, the flügel. His technique on this instrument was even greater than his organ technique. He actually was fonder of the clavichord, an older instrument than the harpsichord, but unsuitable for any purpose but small intimate groups as it played too quietly and the tone did not carry.
As has been noted earlier, the forerunner of the piano had been invented well before Bach's old age, but it wasn't at all popular or much used. It was not until the action mechanism connecting the keys and the hammers was improved that it gained popularity and it still was not like the modern pianoforte (the full name of the instrument -- 'piano' is a shortened name). The improved early model which gained popularity and which was used by Mozart and other musicians of his day, is known as a fortepiano. It had no pedals, hence the technique of playing it was more like the harpsichord or organ technique than the pianoforte. Its tone overall was less powerful but brighter in the upper registers and clearer in the lower than the pianoforte. (Hearing a Mozart piano concerto played on a fortepiano is a real revelation). The addition of the pedals around the turn of the 19th century turned the instrument into the pianoforte and revolutionized the technique since it allowed the player to hold notes with the sostenuto pedal. They were promptly built larger and strung with extra strings for a more powerful voicing, although at the sacrifice of the fortepiano's clarity of tone. Beethoven became probably the first great pianist, followed by Chopin, who was such a master of the instrument that he became a major composer in spite of the fact that he wrote virtually nothing but piano music and, in fact, knew next to nothing about any other music.
