Take your pick! Extant forms when Bach began composing included the Prelude, the Fugue, the Chorale Prelude, the Toccata, several concertante forms, and so on. Bach raised all of them to their highest peak. There is no one best answer, but the "safe" answer is probably "Chorale Prelude".
bach played the organ, along with many other instruments, but bach played the organ the best
Bach played many instruments like the violin, viola, organ, and harpsichord.
i think it was the organ that was used
Bach played the organ, the violin, the harpisichord (which could also be played on the clavichord) and sang in a choir. He also played the viola.
he played organ and piano He also played the harpsichord.
He was a virtuoso organist, who appeared to be more famous as an organist than a composer when he was living. It wasn't until after he died that he was hailed as a genius, and I would say rightly so.Organ and clavier
His main instrument was the pipe organ. He also played the harpsichord.
Bach was most famous as an organist.
Bach played the organ, violin, and harpsichord. Two of his pieces are St. Matthew Passion and Toccata and Fugue in D Minor.
Music composed for and played on the organ was extremely popular during the lifetime of J.S. Bach (which I assume is the Bach being referred to). Master Bach had 20 children. 10 died in infancy and 3 went on to become composers/musicians themselves. None quite equalled Papa Bach, but Carl Philipp Emanuel (CPE Bach) didn't fall too far from the tree.
organ
Bach never played the piano. He played organ, harpsichord and violin. He might have owned a piano in his later years just before his death, but this is debatable.