The bishop of the diocese, Manuel Barrios, turned to the musician Hilarión Eslava, organist, composer and then director of the Royal Chapel in Madrid, who advised him to commission the project for a new organ to J. Merklin, the famous organ maker and pioneer of new movements in the manufacturing of these large instruments with multiple possibilities that made them resemble modern orchestras, and end up overshadowing them.
It was unveiled in July 1857 and was an event of national and international importance. It consists of very complex mechanics which enable the 4000 pipes, distributed over four floors, to sound precise and clear, and from a console that has 63 stops, four keyboards with 56 notes and a pedal keyboard with 30.