How can I transfer music from Mac to iPhone without syncing entire library?

Hello, I have been using the music app on my mac to put songs on my iphone. I only listen to the music on my phone, and so I want to remove the files from my Mac when I upload it to my phone. Since the two devices' libraries are synced, I can't do this without all the songs on my phone being deleted when I transfer new music over. Is there a workaround for this?

[Re-Titled by Moderator]