The teacher reviewing this sentence would point out that since this is a complex sentence, there should be a comma after “song.”
compound sentence, there should be a comma after “realized.”
complex sentence, there should be a comma after “inspiration.”
compound sentence, there should be a comma after “found.”

Hello. You did not enter the sentence which the teacher, presented in the question, needs to review. This makes it impossible for your question to be answered. however, when searching for your question on the internet, I was able to find another question exactly like yours, which had the phrase "As he listened to the haunting notes of the author realized song he had found the inspiration for his next suspense novel." If that's the case for you, I hope the answer below will help you.

complex sentence, there should be a comma after “song.”

Explanation:

A complex sentence is a sentence formed by an independent clause, accompanied by one or more dependent clauses. As you may already know, independent clauses are those that manage to maintain a coherent meaning on their own. On the other hand, dependent clauses are those that cannot maintain a meaning alone and need to have a complement to be coherent. In a complex sentence, the clauses must be joined by conjunctions or commas, which give fluidity to the sentence as a whole.

The sentence presented above is a complex sentence. The dependent clause is "As he listened to the haunting notes of the song." This clause should be linked to the independent clause, which is presented immediately afterwards, with a comma, since a conjunction would not maintain the coherence and fluidity of the sentence. In this case, ideally, place a comma right after the word "song."