Books are my favorite objects to use on the Thing Synth. A cloth cover will dampen the strike to produce a nice mellow tone and the “filter sweep” of opening the cover is really satisfying. I also like applying pressure to the top to get a vibrato effect.

Cardboard boxes get a nice tone and good volume. They’re especially rich for bass notes. The differing surface areas of each dimension will give you interesting variations in tone and the flexibility of the martial allow you to created a vibrato manually.

It’s fun to grab anything you can think of and see what sounds it will make. Metal objects can sound very harsh at lower frequencies but can produce nice tones in upper registers with a beautiful resonance. Plastic containers can sound nice and produce good volume.
I think there could be something interesting with objects like the magnatiles here that let you modify the volume of the resonating object.

These are all balanced on the 4”x4” popper module but we could easily build larger platforms to more securely support bigger objects. Using rubber bands, weights, or various fasteners to hold objects in place can also create more stability.