The simple answer is "It depends". Studio One v3 is capable of utilising any and all standard midi devices you connect to it. Some keyboards do midi over USB and others require a midi 5-pin din connection. Some keyboards can be connected to external synth modules, some can't. The guide for your answer is dependant on what you need from it. Then there is your budget. How many keys do you need? It can be a minefield choosing the right one, I appreciate that, but you aren't forthcoming with specifics. I write this expecting a midi keyboard delivery in the morning, so I am aware that the choices may be a little overwhelming. I started by setting a budget with a 10 - 20% overrun should I need it. I then looked at a few of the sites like Music Radar and similar publications and sites googling by spec. My first controller is unavailable for purchase now - an Alto Professional live 61 key. Simple keyboard but ample for studio one v3. You may get one 2nd hand. My new keyboard is a Roland A800 machine. I can't in good conscience advise either way as I haven't used it yet. The Native Instruments ones seemed interesting, I also researched the Arturia brand. Both come with VST'S. Again, can't recommend them as I haven't used them.
