The hammered dulcimer comes in quite a few different sizes, identified by the number of strings that cross each of the bridges. A 15/14, for example, has two bridges (treble and bass) and spans three octaves. The strings of a hammered dulcimer are most often found in pairs (though some instruments can have up to three or four strings per note). Each set of strings is tuned in unison. A hammered dulcimer requires a tuning wrench for tuning, since the dulcimer's strings are wound around tuning pins with square heads.
The diatonically-based tuning results in most, but not all, notes of the chromatic scale being available. To fill in the gaps, many modern dulcimer builders include extra short bridges at the top and bottom of the soundboard, where extra strings are tuned to some or all of the missing pitches. Such instruments are often called "chromatic dulcimers" as opposed to the more traditional "diatonic dulcimers".
In the Alps there are also chromatic dulcimers with crossed strings, which are in a whole tone distance in every row.
The hammered dulcimer derives its name from the small mallets that players use to strike the strings, called hammers. Hammers are usually made of wood (most likely hard woods such as maple, cherry, padauk, oak, walnut, or any other hard wood), but can also be made from any material, including metal and plastic. In the Western hemisphere, hammers are usually stiff, but in Asia, flexible hammers are often used.
Hammered dulcimers of non-European descent may have other tuning patterns, and builders of European-style dulcimers sometimes experiment with alternate tuning patterns. Versions of the hammered dulcimer are used throughout the world. In Eastern Europe, a larger descendant of the hammered dulcimer called the cimbalom is played and has been used by a number of classical composers, including Zolt�n Kod�ly, Igor Stravinsky and Pierre Boulez, and more recently, in a different musical context, by Blue Man Group. The khim is the name of both the Thai and the Khmer hammered dulcimer. The Chinese yangqin is a type of hammered dulcimer that originated in Persia. The santur and santoor are found in the Middle East and India, respectively.