Well, yeah, when you don't know, you might as well leave it alone and see what happens later so it isn't a case of being ignorant, sure, but when you've experienced it before, you no longer don't know, and that was what I was working off of. You CAN predict, when you've experienced it enough times before that you have a good idea of what the outcome might be. It's good to leave an air of uncertainty, though. Also, if you can't take all criticism into consideration by even a little bit (which was one of the debates earlier), it shows a slight ego, almost, and inhibits your growth, which Socrates wouldn't want.
I think objectivity does exist conceptually, but I also think it can be grasped, in chunks or intuitively without a reason-able explanation, at least. Maritain talks about Art in general (so including music) having a divine interpretation---and thus an objectivity in a sense---during its conception and a human interpretation---since we're able to make mistakes---during its production, like matter and spirit meeting to collaborate (paraphrased). There's a subjectivity-->objectivity spectrum I previously had some idea about that I learned in ethics class last semester, and I'm towards the side of believing in partially grasping objectivity with some subjectivity on the side. For example, two of the ethical positions on the spectrum are nihilism and subjective relativism (yeah, it's morality-based, but a similar analogy applies here).
What I mean by considering what sounds good to you is that you only have a good idea if you're good when you get good (Plato). It's almost like the Paradox of Learning (more Plato); you don't know what to learn unless you know to learn it, or someone teaches you, so you go around somewhat blindly, taking criticism and getting 'taught', until you start to feel like you understand enough to start learning on your own. Now as to when you might really "get"/have a good idea of your distance from objectivity, that's the unknown part, and that's the part where I think the ignorance comes in as a good thing to facilitate your improvement for as long as you live. That way, you'll keep wanting to improve, and as a result you'll keep improving, no matter how slowly.
For me, I WOULD go with what sounds good today, but I wouldn't say that if it sounds good today, it'll sound good a few years later necessarily, even if it might actually be the case. BUT, unlike four years ago, for example, where I would take maybe a year before I would realize there are major flaws in my old, old music, I would know the next day if there's something off in my music, despite it being my own music, and if it's substantial enough for me to need to fix. Heck, zircon polishes his music until it's pretty much perfect, beyond what most people could criticize, and he knows fairly well what he wants in his head, and works until he gets it. So those types of people exist.
So yeah, I think we're both in agreement (or we could reach one) about what Socrates would want.