In the following clips Cormac ó hAodáin discusses aspects of horn construction. The reason the horn is so wrapped up, is that it would be very difficult to transport approx. 17 foot of metal that was just in a straight line. You´d have to have an extremely large car with a very big estate built onto the back.
The horn has a conical bore, which means that it starts small at one end and gradually widens. It´s not conical throughout the whole instrument; it is cylindrical within the valve section. The mouthpiece comes in different shapes and sizes: different diameters right at the small end and the bore of the mouthpiece and the size and depth of the lip of the mouthpiece can be wider or less wide. The way it works is that by buzzing my lips against the mouthpiece I cause the air inside the instrument to vibrate and the sound resonates from that.