bout the Portative Organ
Most wind instruments use air that is expelled from the player's lungs. Organs differ from such instruments in that they use bellows or similar mechanisms to supply a stream of air. They also differ from most wind instruments in that they have a pipe for each pitch they can produce rather than having a single pipe produce several pitches by uncovering holes to effectively shorten the length of the pipe. Organs are characterized by their use of keyboards, or slides to activate the flow of air to a given pipe.
Despite their relative complexity, organs are fairly old. They were described by the first century writer Hero of Alexandria, and predate him by several centuries. Such early organs were not powered directly by the pressure generated by the bellow or piston. Instead, the bellows blew air into an inverted bowl, called a pnigeus, that was submerged in water in a sealed cistern. The air would displace the water, raising the level of water in the cistern. The pressure of the water on the air would power the instrument. By the Medieval era, water organs had fallen out of use.
Historically organs were made in a variety of sizes. The largest ones filled large rooms, and had hundreds of pipes. There were many fairly small organs, that measured approximately three feet wide, by three feet tall, by two feet deep. Such organs are portable, and have at times been referred to as portative organs. However, in almost all cases, portative organs refer to a still smaller instrument that can be carried by a single person. In fact, they can be played while they are being carried.
Portative organs are typically less than two feet long, less than a foot deep, and approximately two and a half feet tall. There is a keyboard on one side of the instrument, and a bellow on the other. The player uses his right hand to operate the keys, and his left hand to pump the bellow. The pipes emanate from the top of the instrument, and were typically arranged in one or two rows. They differ in length and give it a sloped appearance.
The keyboards of early portative organs consisted of buttons rather than keys. In some instruments these looked very much like checker pieces. In others, the buttons looked like small rounded squares, very much like a piece of Chicklet gum. Somewhat more traditional keys came into use in the fifteenth century. Even these keys were much shorter than the keys on a piano, measuring only approximately two inches in length.
Organ pipes were traditionally made from metal. Very early pipes were made of copper. By the middle ages lead was one of the metals used in the alloys used in organ pipes. It continues to be used in this fashion to this day. When resources were lacking, the pipes were fashioned from wood. Such occurrences did not seem to occur until the sixteenth century.
Unlike larger organs, portatives have a single set of pipes. It simply would not have been practical to include several sets of pipes on such a small instrument. The pipes on portative organs were generally at two foot pitch. Some instruments had pipes at one foot pitch.
Portative organs can play polyphonic music, unlike most wind instruments, as they have a pipe for each pitch they can produce. However, they do not have the capability of producing polyphonic music that is possessed by a larger organ. Unlike larger organs, the bellows on portative organs allow the player very precise control of the flow of air, and allow for a great deal of expression. This expression is not quite as great as that on a mouth blown instrument. Thus we see that portative organs reside in the space between fully polyphonic instruments and expressive wind instruments.