J. S. Bach (1685-1750) was a German Baroque composer who is revered for the originality and skill of his contrapuntal and harmonic techniques. He spent most of his life working as an organist and choirmaster, but was also employed as a composer a many different Royal Courts. However, his skill as an organist and composer for Organ is what gained him the reputation he enjoyed during his lifetime.
This is perhaps epitomised by his Fantasia and Fugue in G Minor (BWV 542), often referred to as the Great Fantasia and Fugue. It has been edited by Sir Frederick Bridge and James Higgs.