[cperciva]

Some people have suggested putting speakers inside violin cases for exactly this reason -- but I doubt it would work. When a violin is played, the wood vibrates far more than the surrounding air (if it didn't, energy wouldn't be transferred from the violin to the air) so in order to get the same amount of vibration in the instrument, you'd need very loud speakers.

[nothingmuch]

A vibrator has a pretty good form factor for insertion into a loaf of bread =)