“The soprano is a small violin, with strings of a length suitable to be tuned a fourth above the ordinary violin. It existed in its own right for playing notes in a high compass... It survives as the ‘three quarter violin’ for children. Tuned like a violin, it sounds wretched, but in its proper pitch it has a pure tone colour of its own, for which the high positions on the ordinary violin gave no substitute.” (Grove’s Dictionary of Music and Musicians).
J. S. Bach wrote music for an instrument in this tuning.
Tuned an octave above the alto, the soprano was designed to have as large a plate area as possible, with resulting shallow ribs and fairly large f holes to raise the cavity resonance to the desired G at 392 Hz. The mensure is as long as possible for playing convenience.