Tanpuri
The tanpura you can actually carry.
A smaller body, four or five strings, and a lighter, higher drone that goes to lessons and concerts without a car. Sitarists and sarod players often keep one tuned to their own key, and vocal students use one wherever a full-size instrument will not fit.
Tanpuri or full tanpura? Size and depth. The tanpuri's smaller body gives a lighter drone sitting higher; a concert tanpura fills a room. The function, holding a steady drone behind practice and performance, is identical. Many players eventually own both.
How is it tuned? Like a tanpura, typically Pa Sa Sa Sa, adjusted by raga, at your own pitch. Tell us your Sa and we tune it before dispatch.