Today I played a concert in Bushnell Park in Hartford. Near to the stage where my group was playing, there was what appeared to be a large power generator that was making a constant, low rumbling background noise. While the noise of the generator was really minimal and hardly noticeable, it was having the oddest effect on my bass. Whenever I took my fingers off the strings, my bass would start echoing the rumbling noise. I looked over and sure enough, the D-string was vibrating wildly and getting louder by the instant. I muted the string, it stopped, then I took my fingers away again and the same thing happened over and over! Has anyone else ever experienced this? I'm thinking something about my open D string was in perfect sync with the generator, or something.... But it sort of freaked me out and I don't fully understand what was going on. It was funny though. While we were warming up, I said to the sax player, "Look! I can play with no hands!" He was pretty impressed when the D started itself up and got progressively louder until it seemed my bass was about to break.