Transferring only a few songs in Music, without losing all the rest.

I want to transfer only a few music files from my Mac to my iPhone. If I sync the two devices, all Music files are transferred, creating many duplicates. In the past, when I selected a few files to "sync," all other music on the iPhone was deleted.

Is there a way now to move just new music files from the Mac to the iPhone without copying all of them or losing most of them?