I use a program called Reason 7 from Propellerhead Software and it is available for both Windows PCs and Mac PCs.
It is not free, but the full program can be downloaded and used in Demo mode.
It can be used without having any other devices.
Over the years, I tried several other programs, but Reason seemed to suit my way of doing things the best due to it's instrument rack based layout.
Like most programs, to get the most out of it you will need some other devices to get your audio into the PC and although you can use the PCs sound card, you will probably need to invest in at lease three devices that I can think of.
- An audio interface unit. (I use a Focusrite Scarlett 8i6)
- A good pair of headphones.
- A midi keyboard (I use a Nektar Panorama P4 because it is designed to work seamlessly with Reason)
You can look up all these items on the web to get their full information.
The other important point is that all these items, including the Reason software are reasonably low cost, but IMHO of high quality.
Overall of course, this is a huge topic and there are many programs and devices available in use, but this is as good a place as any to start.
I hope you find this helpful.