One of the readers of the blog wrote to me recently about the usage of a real Tanpura versus electronic shruti boxes.

I must say having a well tuned tanpura resonating near your ear helps in recognizing and consolidating harmonies (its the same reason why avergae singers sing a lot more in tune in a 4-part choir). However, tuning, bridging and threading, apart from finger pressure and positioning, make tanpura playing an art; if you have not done it for a long time, it is not as easy to learn as it would seem. It might actually be quite cumbersome if you are in the middle of learning vocal technique.

Before buying a Tanpura try this