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.
Hurdy-gurdy to keys that change the vibration length of the string, much as a guitarist uses his or her fingers on the fretboard of a guitar. In the earliest hurdy-gurdies these keys were arranged to provide a Pythagorean temperament, but in later instruments the tunings have varied widely, with equal temperament most common because it allows easier blending with other instruments. However, because the tangents can be adjusted to tune individual notes, it is possible to tune hurdy-gurdies to almost any temperament as needed. Most contemporary hurdy-gurdies have 24 keys that cover a range of two chromatic octaves. To achieve proper