software synths.
get a good program. i reccomend Reason 3.0 or FL6. FL6 is easier to use, but very limited. reason is much deeper, harder to use, and has a wealth more variety.
essentialy, the difference is taht instead of turning a knob, you use your mouse, and instead of carrying a box, you carry your computer.
and its torren^H^H^H^H^H^H easy to buy.