Like the cello, the bass viola da gamba is part of a family. The smallest, highest-sounding member is a treble viol, equivalent to the violin. Next larger and deeper in tone is the tenor viol, approximately equivalent to the viola. Even larger and deeper-sounding is the bass viol, equivalent to the cello. The largest, deepest size, the double bass, is the only viol played in orchestras today.
Viols have a long history.
Shakespeare mentions them in several plays, including Twelfth Night. The sound of the viol is sweet and shimmering, quieter than that of violins, violas, or cellos. Viols smaller than double basses are, in fact, too quiet to be effective in large orchestras or big concert halls, which is why they are no longer very common. But many people today love the particular timbre of viols and the Renaissance and Baroque music written for them. Concerts are usually given in small halls or churches, which suit viols well.