It’s nice to have music in the shop. This device was made to turn a wall into a speaker, by fastening it behind a wall to the wallboard. The round pads on the ends of the legs are glued to the wall, and the middle section is like the middle of a speaker, minus the cone, and presses against the wallboard, vibrating it.
This is the way sound is invisibly produced for museum displays. Violins will work instead of walls, but as with speakers, if you need some bass, you need a larger thing to vibrate. A cello will add that to the mix. Supposedly this kind of artificial playing is supposed to help break in a new instrument, but I haven’t noticed any improvement from this particular method, which is one of several things I’ve tried for aging tone without the musician’s input.