I'm collaborating with a friend right now. Anyway, the sentence in question is this: Children, as usual, race down the streets, oblivious laughter echoing hollow in the steel. My friend thinks it should be like this: Children, as usual, race down the streets, oblivious laughter echoing hollowly in the steel. Now, I know that correct grammar would mean I should use "hollowly", the adverb. But sometimes I like to switch what should be adverbs to nouns - as I've done by writing "echoing hollow" as opposed to "hollowly". I see it as poetic license. It's not that I don't know the correct grammatical conventions. I simply prefer the rhythm of using "hollow" in the sentence. It's stark, it jumps out at you. It's not smooth but that's how I want it. My friend, however, sees it as a "glaring mistake." So... thoughts? Is it okay to use poetic license in this and keep "hollow"? (and if yes, does it work for you?) Or is my friend right and it's just weird and I should just change it back to an adverb?