here is a great quote from Robin Whittle, creator of the Devil Fish modification for the TB-303. Don't worry if you can't understand the electronics technobabble, there are some real gems in here.

The Devil Fish does not have an external oscillator, but it does have an external input. The Devil Fish principle is for a single chain of processes (not two oscillators in parallel) to be doing things which range from "electronic naturalesque" to "mechanical overdrive" - through the use of unusual circuitry, high signal levels, and in one case, a filter FM feedback system which can elegantly approach chaos. Those who recognise that complex things like a love life can benefit from wise or reckless overloading of certain elements (for instance a hard spanking) are well on their way to understanding the Devil Fish. In this case the filter is driven well beyond normal limits. Like an ultimately appreciative spankee, its noises and gyrations provide depth, complexity and emotional heat which is exciting and highly satisfying for all concerned. (As when any gentleman heats up a derriere, there is no permanent damage.) Boosting the oscillator level to 20 times normal was good, but there was a promise of even greater excitement at even higher levels. I decided this called for the clothesbrush treatment and whilst examining various combinations of standard resistor values, decided that the pair which gave 66.6 times the normal level was the most auspicious. (Gentlemen, if you think that all that women want is what they say they want, then you need to read some romantic spanking fiction written by women, for women. An excellent source is "Sassy Ladies Magazine" - PO Box 4516 Lexington, KY 40544 USA US$12 for a sample issue. From their advert - "Independent, feisty women find they still need strong, caring men.")

Right then.

Time to start modding.

I'm actually in the process of looking at the Devil Fish modifications, and seeing how I could implement my own, and even looking into other mod ideas. All this is on my x0xd0x wiki, specifically the mods section.