Seems to me that everyone is hung up on the word, "Musical", and are not answering the man's question. If you read the original post, he wants to know what makes a system good! He just uses the word Musical for the lack of a better one. So, what makes a system good? That's a very simple question to answer. A good stereo system is one that compels you to listen. One recording leads to another, and another, and you find it hard to pull yourself away from it.
Let me elaborate, as a young man, even as a child, I pursued a good stereo! And when I was 16 I had a nice Technics receiver that just impressed my friends to no end. It was quite nice for the time, and for someone my age. But I was always looking for something better. I wanted to move up to a really high end stereo! I went through a few different setups, mostly Japanese receivers of the era, and was never satisfied. And then one day I found my way into a real high end salon! I was officially enlightened. I was still fairly young, not wealthy, and I assembled a system over a few years consisting of an Adcom 555, Adcom pre-, Sony ES CD player, Denon record player, and Vandersteen 2C speakers. This simple little system was musical! In that it got my foot tapping, it could evoke an emotional response! I could easily become so involved that it would bring a tear to my eye. And I played music! I would come home from work, turn it on as soon as I came in. After supper I would play records, one after the other, all night, it would pass midnight and knowing I had a hard day tomorrow and I just had to hear one more record! And many, many times I wouldn't get to bed until the wee hours of 2 or 3am, I just couldn't pull myself away.
Well, I have a different life now. I live in a different house, different wife, different job, everything. And I no longer own that little $5 or $6K system, now I've got a system, all used from Audiogon of course! With about $17K in it! It's bigger, fancier, and made up of much better names than that early system, and it sounds fantastic! It sounds amazing, but, for some reason that desire to keep playing one more record, that inability to pull myself away from it, is gone. I often wonder if it's just me? And maybe at some level it is. But I keep swapping gear out, trying to recapture that musicality of the old system. And I'm getting closer! But still. Not quite there. Why don't I just sell it all and buy an identical system to that early system? I'm not sure. But that's not what I'm writing about, I'm writing about what makes a stereo musical! And to me, that is the definition.