Any Registration of a Song for Copyright seems to trigger the notice of the scammers who begin to contact you.
They have not heard the Song, seen the sheet music, read the Lyric.
They simply know you thought enough of it to Register it and may think they've taken an interest because they 'believe' in the Song.
They don't. They can't. They don't know any more than that YOU thought the Song merited Copyright protection.
There are legitimate Arrangement & Repertoire men/women seeking Songs for Publishers, for Artists' management, but they're not likely to 'find' you. They search Publishers, each other, music libraries. Some may take occasional forays into Youtube and other places where people put Songs. But they are likely as uninterested as the average listener who seldom finds a 'hit' there.
Follow up on any contact, of course. The one legitimate contact looks just like all the scammers. So a little investigation is worth doing. But when they change the story from "looking for Songs" for singers, to "How much ya wanna spend?" you can stop the conversation. That's trying to sell you something instead of buy something from you.

There will always be another song to be written. Someone will write it. Why not you? www.garyeandrews.com