What message about challenges does the author express through "Sweet, Difficult Sounds"?

The challenge expressed through these is the challenge of difficulty of the language to express the meaning.

Explanation:

The words such as "Sweet, Difficult Sounds" are used as deceptive words whose meaning is not very clear, they are not easy to understand. The poet sometimes has to search for new words to express the meanings in a better way to the reader.

These are the words which are thought to be sweet but do not show what they actually want to show. Hence the people can not understand what the words mean.