Hurdy-gurdy twenty-three different forms, and there is still no standardized design today. The six-stringed French "vielle à roue" is the best known and most common sort. A number of regional forms developed, but outside France the instrument was considered a folk instrument and there were no schools of construction that could have determined a standard form. There are two primary body styles for contemporary instruments: guitar-bodied and lute-backed. Both forms are found in French-speaking areas, while guitar-bodied instruments are the general form elsewhere. The box form of the "simphonia" is also commonly found among players of early music and historical re-enactors.
Music technology made metal strings possible. Bowed strings were used as well. The bowed lyra of the Byzantine Empire was the first recorded European bowed string instrument. The Persian geographer Ibn Khurradadhbih of the 9th century (d. 911) cited the Byzantine lyra as a bowed instrument equivalent to the Arab rabāb and typical instrument of the Byzantines along with the "urghun" (organ), "shilyani" (probably a type of harp or lyre) and the "salandj" (probably a bagpipe). The hurdy-gurdy was a mechanical violin using a rosined wooden wheel attached to a crank to "bow" its strings. Instruments without sound boxes like the jaw