Sounds much better than my attempt at the same thing. Do you have any random modulation on your hum? I found rolling the base of the hum up and down a bit over a time of a couple of seconds added a bit of life. You can do it on a slow sine, or get a bit more creative and execute a random walk (pick freq, slew to it slowly, pick new random freq within sensibe range). Or get really clever and use perlin noise, either generated or from an array long enough the ear doesn't pick the pattern.
Your hum is much better than anything I've got so will be interested to see how you constructed that.
Edit: also impressed you can wave a breadboard around without firing the wires out of it!