MOTM

I've always thought that transducers were another name for pickups, and doing 
an internet search that seems to be what they are. They convert an acoustic 
vibration into an electrical signal. But when reading about the old Ondes 
Martenot keyboard instrument, they say that one of the speakers (or diffusers) 
uses a transducer to drive the strings on one of these diffusers. Is there a 
device that I can use that takes an electronic signal and converts it into an 
acoustic vibration for setting a string in motion or driving the bridge of an 
acoustic instrument? Something other than a speaker that is. I'm still thinking 
about setting a violin in motion using a synthesizer.

-Elhardt