Well, I call it a thumping sound. It's the sound in my mind that I want to get out of my bass. I bought a Pandora PX5D that lets me tap into different amp and cab sounds. It's a poor man's substitute for the modeling head I can't afford. But even it doesn't get me that sound. Here's the crazy part: I can get the sound if I let the soft side of my hand rest on top of the strings near the bridge. But then I can only play with my thumb. I've heard that famous session bassist Carol Kaye did something similar like sticking a piece of foam rubber up under the strings right where they came off the bridge. Now, I'm trying to figure out a good place to buy some similar material. It'll save me the trouble of an electronic solution to this challenge.