What is the largest instrument of the bass-viol kind, having strings tuned an octave below those of the violoncello; the contrabasso; -- called also double bass. [Written also violono.] called?

violone — The largest instrument of the bass-viol kind, having strings tuned an octave below those of the violoncello; the contrabasso; -- called also double bass. [Written also violono.]. (Webster's 1913.)