Depends entirely on your needs basically. Sampled beats or like some sort of mpc workflow then even a tablet would suffice, And I'm talkin 1.3ghz atom lol.
But for stuff like synthesis and multiple tracks and layering, effects and automation or building modules, depends entirely on workflow.
In general though using a low end tablet as an mpc is actually pretty funnily decent.
But Ideally a machine with a minimum of 8gb of system ram,a processor that is an A6 or above in tier and a good harddrive. 7200rpm, not advised to go below that speed.
Clock speed is proportionate to how intense things get.
Alotta of stuff going on=faster proc needed.
If you not a builder then any cyberpower desktop or avatar desktops imo. Not fond of alienwares at all.