Once you've gotten Aristocrat papers and shown them to Ms. Charm, she'll want a song. To get this, you go to Vagner (the poet in the tavern). Before he'll give you the song, he wants some liquid creativity. You end up with a recipe that is booze plus three red mushrooms. Hopefully you've already unlocked the tech to make booze (if you're like me and wondered why it was there, here's the answer). You can make booze with three wine, or other options, and then make the quest beverage with the booze and mushrooms (walk over to the swamp and pick three).
When you bring the bottle back to Vagner, and do it immediately, he'll say he needs some time. Give it a day or so and go back. He'll be gone but will leave a note telling you to find him at the seaside cliffs at night.
Once it's dark, to to the northeast corner of the map. I went to the shore, then north to the circular upper area, and then wander in the pack of bushes just up and right from the middle to trigger the cutscene. Once it's done, you'll have your song.
HOWEVER, the achievement pops when you give it to Ms. Charm (so don't be worried like I was)