The role of the two instruments when used as accompaniments is different as well. The piano works well as a leading instrument- the power of percussion instruments comes from the first strike. The piano can also produce rhythms and melodies much faster than an organ, making it an excellent introduction piece. Likewise, it is also a good tool for guiding the melody. An organ is capable of filling a larger space with sound, and supporting a large congregation, for example, in singing. It achieves its power during the sustainment of the notes. A primary function of an organ is to fill in sounds and provide the supporting chords.
During the Romantic period, the organ became more symphonic, capable of creating a gradual crescendo. New technologies and the work of organ builders such as Eberhard Friedrich Walcker , Aristide Cavaillé-Coll , and Henry Willis made it possible to build larger organs with more stops, more variation in sound and timbre, and more divisions.  Enclosed divisions became common, and registration aids were developed to make it easier for the organist to manage the great number of stops. The desire for louder, grander organs required that the stops be voiced on a higher wind pressure than before. As a result, a greater force was required to overcome the wind pressure and depress the keys. To solve this problem, Cavaillé-Coll configured the English " Barker lever " to assist in operating the key action.