String instrument rosin than players of lower-pitched instruments, who tend to favor darker, softer rosin. The ravanahatha is one of the oldest string instruments. Ancestors of the modern bowed string instruments are the rebab of the Islamic Empires, the Persian kamanche and the Byzantine lira. Other bowed instruments are the rebec, hardingfele, nyckelharpa, kokyū, erhu, igil, sarangi and K'ni. The hurdy-gurdy is bowed by a wheel. Rarely, the guitar has been played with a bow (rather than plucked) for unique effects. The third common method of sound production in stringed instruments is to strike the string. The piano and hammered dulcimer use
Hurdy-gurdy intonation and sound quality, each string of a hurdy-gurdy must be wrapped with cotton or similar fibers. The cotton on melody strings tends to be quite light, while drone strings have heavier cotton. Improper cottoning results in a raspy tone, especially at higher pitches. In addition, individual strings (in particular the melody strings) often have to have their height above the wheel surface adjusted by having small pieces of paper placed between the strings and the bridge, a process called "shimming". Shimming and cottoning are connected processes since either one can affect the geometry of the instrument's strings. In some