Personally I only really know of some digital music workstation, but that can be a bit tricky to learn. If you can find a trial version of Magix music maker 14 or 2008 that was quite cool actually. Besides that there's Sony ACID, FL Studio, Albeton live, but if you want a free alternative you would need to use Lmms. Of course there's also the old MTVMG if you got a PS1 emu with the right plugins, but it won't let you make your very own sounds as much.