The cane reeds change pitch as the moisture levels change, meaning that as they are played they go out of tune. Until recently drone reeds were also cane but now many pipers have replaced cane reeds with synthetic reeds. Cane drone reeds are incredibly unreliable; they could stop working without warning and also change pitch as they are played. Synthetic reeds are much more reliable, they are easier to use and don't change pitch meaning once the drones are tuned to each other they will stay there and only have to be tuned to the chanter. Materials Highland pipes were originally constructed of such locally available woods as holly, laburnum, and boxwood. Later, as expanding colonisation and trade provided access to more exotic woods, tropical hardwoods including cocuswood (from the Caribbean), ebony (from West Africa and South and Southeast Asia) and African blackwood (from sub-Saharan Africa) became standard in the late 18th and early 19th century. In the modern day, synthetic materials, particularly Polypenco, have become quite popular, especially among pipe bands where uniformity of chanters is desirable. Ornamentation on stands of pipes can be made from: ivory, horn, nickel, German silver, silver, stainless steel, imitation ivory (often catalin or possibly bakelite depending on the year the pipes were made), or other exotic woods. Music The Scottish Gaelic word literally means "piping", but it has been adapted into English as piobaireachd or pibroch. In Gaelic, this, the "great music" of the Great Highland bagpipe is referred to as ceòl mòr, and "light music" (such as marches and dance tunes) is referred to as ceòl beag. Ceòl mòr consists of a slow "ground" movement () which is a simple theme, then a series of increasingly complex variations on this theme, and ends with a return to the ground. Ceòl beag includes marches (, , , , etc.), dance tunes (particularly strathspeys, reels, hornpipes, and jigs), slow airs, and more. The ceòl mòr style was developed by the well-patronized dynasties of bagpipers MacArthurs, MacGregors, Rankins, and especially the MacCrimmons and seems to have emerged as a distinct form during the 17th century. Compared to many other musical instruments, the Great Highland bagpipe is limited by its range (nine notes), lack of dynamics, and the enforced legato style, due to the continuous airflow from the bag. The Great Highland bagpipe is a closed reed instrument, which means that the four reeds are completely