He believes himself to be God's chosen instrument.

相信自己是上帝选派的执行者。

After that, the musician chooses instruments to play the song.

然后，编曲老师再挑选演奏这首曲子的乐器。

We cannot, indeed, give them credit for either great sagacity or goodness, else they would have chosen more noble instruments, when they wished to show themselves the benevolent friends of man.

的确，我们不能称赞他们的智慧或善良，否则当他们希望向自己展示人类仁慈的朋友时，他们会选择更崇高的工具。