Are you using an internal tone generator or an external drum machine ? If you are using an internal (plugin) you can do it with out hooking up anything using cakewalk. Exactly how will depend on the software. However if you are using a drum machine, the way I do it is to have the drum machine driven by the computer and take an audio line out of the drum machine and into a regular audio input of your interface / sound card and recording it as an overdub or what ever.