Organists are often asked these two simple questions . . . the answer, however, is both simple and complicated! I offer you my best shot at answering clearly and simply!
What is an organ? The very first organs were winded through the use of moving water and were popular in Greek civilization to provide a “drone” (like the drones of the bagpipe) as background for entertainment instruments and singing. In settings more closely associated with organs (i.e. churches), the instrument is thought to have made its first appearance as early as the 6th century. By that time, it had grown from its humble, water-winded system into a much larger instrument (still small by today’s standards) which was raucous in nature and whose function was principally to play during formal processions and, to a lesser extent, to accompany singing.
Towards the 13th century, the organ took on a much greater liturgical (sacred) role – offering support for chant and presenting specific music written for it (albeit geared towards the Mass). Because of the increasing importance being placed upon it, the organ also grew in size! It was winded by multiple bellows (often worked by multiple individuals); its palette of stops (collections of pipes of varying timbre and pitches) increased; and it became an increasingly important work of art in the life of both church and community.
By the 15th century in Germany, organs were being built with separate stops and keys for the feet – the pedalboard was born. The organ continued to develop into styles that reflected the national identity of the builder: e.g. Dutch organs sounded different from English organs, which sounded different from American organs, etc. These nationalistic styles were also heavily informed by composers for the organ as they pressed builders to create new and innovative sounds for the organ. Additionally, the organ began to appear in town halls, orchestra halls, and opera houses as composers included parts for it in their works: think of the heroic Symphony No. 3 of Camille Saint-Saëns or the stunning Concerto for Organ by Francis Poulenc, to name but a few.
How does it work? Well, first of all, an organ is basically a collection of very expensive whistles (pipes) of varying tonal colors that speak (make sound) when air blows through them. How the pipes are controlled from the keyboards (console) varies from builder to builder, but there are basically two ways for that “connection” to be made. Some organs are called “tracker organs” as they have an actual physical connection through levers, cables, and joints — all making up the tracker mechanism — which runs from each key to the base of each pipe, while other organs are called “electro-pneumatic organs” because that key to pipe connection is made NOT with trackers, but rather through electronic signal transmitted through a wiring system (and in some cases, involving a computer!)
For example, in Chicago, the organ in the balcony at Holy Name Cathedral is a tracker organ built by a Dutch builder (Flentrop), while the St. James’ organ is an electro-pneumatic organ built by American builders (Austin and E.M. Skinner — and a few others!) St. James has had an organ since the church was first built in 1837; over the years, it has been rebuilt and enlarged many times and currently consists of 99 ranks (collections of pipes) and over 5800 individual speaking pipes. Most notably, it incorporates the historic 1929 E.M. Skinner Organ originally built and installed in Chicago’s Lyric Opera House.
– Bruce J. Barber II