[Gurthang]

Yes, I very much agree with Heren on this. The above quote by davem says 'amid the... world' but 'beyond the Music'.

Perhaps it is like davem's road theory, but slightly different. Elves, Valar, Maiar, and all others have to follow the points that Eru has designed. They may take different paths to reach those points, but they still go to those places. Men are exactly the same in that respect. They have choices to make, forks to choose, but still come out where Eru planned. That would be 'amid the powers and chances of the world'.

But the choices they make affect the hereafter. Each fork they choose is presumably either good or bad. Which one they choose will make them more good or more bad. Once they die, those choices that they make will determine what happens to them. They would at that time be outside the Music and would have chosen their own path beyond what the Valar sang. This would explain the 'shape their life,..., beyond the Music of the Ainur'.

So men live exactly the same as all the other inhabitants of Middle-Earth, only that the choices they make affect their afterlife.