structural:reformatting, information:classification
Medieval

From 800 to the 1400s, the use and construction of organs developed in significant ways, from the invention of the portative and positive organs to the installation of larger organs in major churches such as the cathedrals of Winchester and Notre Dame of Paris. In this period, organs began to be used in secular and religious settings. The introduction of organ into religious settings is ambiguous, most likely because the original position of the Church was that instrumental music was not to be allowed. By the 12th century there is evidence for permanently installed organs existing in religious settings such as the Abbey of Fécamp and other locations throughout Europe.

Several innovations occurred to organs in the Middle Ages, such as the creation of the portative and the positive organ. The portative organs were small and created for secular use and made of light weight delicate materials that would have been easy for one individual to transport and play on their own. The portative organ was a "flue-piped keyboard instrument, played with one hand while the other operated the bellows." Its portability made the portative useful for the accompaniment of both sacred and secular music in a variety of settings. The positive organ was larger than the portative organ but was still small enough to be portable and used in a variety of settings like the portative organ. Toward the middle of the 13th century, the portatives represented in the miniatures of illuminated manuscripts appear to have real keyboards with balanced keys, as in the Cantigas de Santa Maria.

It is difficult to directly determine when larger were first installed in Europe. An early detailed eyewitness account from Wulfstan of Winchester gives an idea of what organs were like prior to the 13th century, after which more records of large church organs exist. In his account, he describes the sound of the organ: "among them bells outstanding in tone and size, and an organ through bronze pipes prepared according to the musical proportions." This is one of the earliest accounts of organs in Europe and also indicates that the organ was large and more permanent than other evidence would suggest.

The first organ documented to have been permanently installed was one installed in 1361 in Halberstadt, Germany. The first documented permanent organ installation likely prompted Guillaume de Machaut to describe the organ as "the king of instruments", a characterization still frequently applied. The Halberstadt organ was the first instrument to use a chromatic key layout across its three manuals and pedalboard, although the keys were wider than on modern instruments. The width of the keys was slightly over two and a half inches, wide enough to be struck down by the fist, as the early keys are reported to have invariably been manipulated. It had twenty bellows operated by ten men, and the wind pressure was so high that the player had to use the full strength of their arm to hold down a key.

Records of other organs permanently installed and used in worship services in the late 13th and 14th centuries are found in large cathedrals such as Notre Dame, the latter documenting organists hired to by the church and the installation of larger and permanent organs. The earliest is a payment in 1332 from the clergy of Notre Dame to an organist to perform on the feasts St. Louis and St. Michael. The Notre Dame School also shows how organs could have been used within the increased use of polyphony, which would have allowed for the use of more instrumental voices within the music. According to documentation from the 9th century by Walafrid Strabo, the organ was also used for music during other parts of the church service—the prelude and postlude the main examples—and not just for the effect of polyphony with the choir. Other possible instances of this were short interludes played on the organ either in between parts of the church service or during choral songs, but they were not played at the same time as the choir was singing. This shows that by this point in time organs were fully used within church services and not just in secular settings. Organs from earlier in the medieval period are evidenced by surviving keyboards and casings, but no pipes. Until the mid-15th century, organs had no stop controls. Each manual controlled ranks at many pitches, known as the "Blockwerk." Around 1450, controls were designed that allowed the ranks of the Blockwerk to be played individually. These devices were the forerunners of modern stop actions. The higher-pitched ranks of the Blockwerk remained grouped together under a single stop control; these stops developed into mixtures.