I really love this instrument.
Favoured by Joseph Haydn’s employer, Prince Nicholas II of Esterházy, the Classical baryton is similar to a bass viol in having 6 bowed strings, frets and the same tuning, but has the super fun addition of 10 (in the case of my instrument) metal strings which run behind the fingerboard. These extra strings both vibrate sympathetically and are at times used as part of the melody, plucked by the left hand thumb. The sound is amazing! My baryton was made by Henner Harders, and is a copy of one by Daniel Agnatius Stadlmann, Vienna, 1732.