求这句英文的句子成分分析，不要翻译，翻译我会，就是分析句子成分，是啥从句啥的

Question

Heaven knows it is difficult enough to say precisely what it is that a piece of music means.

Answer 1

Heaven knows it is difficult enough to say precisely what it is that a piece of music means.

it is difficult enough to say precisely what it is that a piece of music means是knows的宾语。

to say precisely what it is that a piece of music means是动词不定式做宾语从句中的真正主语。

what it is that a piece of music means当say precisely的宾语，也就是宾语从句，同时也是含有特殊疑问句的强调句形式。

强调句还原：it is what that a piece of music means.对what强调。

强调句的结构是：it +被强调部分+that+剩下的句子成份。正常顺序是：

a piece of music means what.