The Persian santour is the original form of the hammered dulcimer (traditional hammers are illustrated). The middle bridge divides the strings at a ratio of the octave 1:2. In the original construction there are adjustable bridges instead of the single middle bridge.

This feature allows the player to change the tuning of the instrument within minutes to different modal scales even with quarter-note intervals. Because the bass strings are usually brass whereas the strings over the middle bridge are steel, the sound character of the santour is distinguished through a mix of the warm ground tones of the bass and the sharp metallic sound of the upper strings.
 
The resonance board of the traditional instruments is usually made of hard wood, for instance walnut. The santour is particularly suitable for improvised music. There are 72 strings over two sets of 9 bridges on each side producing 27 diatonic tones, a little over 3 octaves or sometimes 4.