As a longtime Rolemaster player who escaped into 3rd Edition to avoid overmuch emphasis on "reality," I can only shake my head at this whole discussion.
I refer everyone to
www.theguildcompanion.com or any other Rolemaster web site where you can discover long standing arguments as to what makes sense and how to more realistically capture some minor detail of combat or skills in that game. Sure, there's a good reason for saying the perform skill is not the same for everything (we've all seen singers in bad movies, and actors sing bad songs), but the overdivision of skills is not a good thing.
Trust me, general categories suffice very well even for the heavy RP crowd. It took me a long time to realize that the more you divide a character into the skills the less you focus on the personality involved. Maybe splitting perform into 2 or 3 skills would be okay or use the penalities suggested for the Ride skill in some manner. I find it hard to believe that a small subset could not be derived for the various perform to keep it in line with the other skills - and even for the heavy RP crowd - perform is not a primary skill. I say this in relation to the rare occurence or need of this skill to solve problems typical for an adventure. It's neat and cool and can be used, but it is rarely that central to a plan or course of action.
My only point is that the overdivision of skills is a nasty slope of vastly slippery composition. Rolemaster had/has the following skills that all fit within heal: first aid, second aid, surgery, diagnostics, use prepared herb, remove poison, and others were possible. There are many such examples all based on the idea that it's possible to know one subset without the other even if that would be rare. If you need this for RP reasons, then just impose the limit on yourself.
Come on now, skills are good and cool, but don't get carried away.