Undertune AU – Like Dancetale but with Music (each monster has their own theme song/sings to express their soul, and it's part of their magic. Examples: their battle music is actually part of their attack, they express their SOULs with music, combine with another's to show affection etc.)

It had been a year since Frisk had climbed Mt. Ebott and fallen down, finding themselves on the adventure of a lifetime and, at the end of it all, with a new family and home and more people who cared about them than they had ever thought possible.

All the rumors Frisk had heard about the monsters under the mountain hadn't prepared them for what they'd encountered, down there in the underground.

But most of all, they hadn't been prepared for the music.

It seemed that every monster had a theme song, one that their magic played for them, modifying itself to match their mood but still recognizably theirs. And each one of them seemed willing to burst into song at the drop of a hat, to the confusion and sometimes embarrassment of the humans around them.

Well. Almost each one of them.

In the year that they'd been above the mountain, Frisk still had yet to hear Sans sing a single note. His music was subdued when he thought no one was looking, though bright and cheerful (and sometimes a little obnoxious) whenever anyone else was around.

Frisk, though, was good at sneaking, and had caught Sans a few times when the skeleton was alone, and they wondered.

Their new mom said that a monster's song could bring a closer connection between two monsters, or even a monster and a human who sang together, as their SOULS resonated to one song made by two merging to a harmonious whole. That it was the most pure way for them to express themselves.

Right now, the huge backyard of the Big House (the home Toriel had bought, since it seemed the gold that was the Underground's main currency was worth more on the surface than the monsters had dreamed, so she took the first indulgence she had had in years and bought a house that could hold all of Frisk's adopted family at one time, along with a yard big enough for even Undyne's games) was filled with monsters, all here to celebrate the one year anniversary of their freedom.

Papyrus had been grilling, but thankfully (his cooking had improved, but he and Undyne still mistook 'passion' for 'skill') he'd been distracted, and Grillby had taken over, despite Toriel's protests that he shouldn't have to cook on his day off.

Frisk wandered off to find Papyrus. His music was bright and cheerful, like usual, but it was harder to find than normal, since everyone's music was reflecting a similar mood.

Still, they found him eventually, and tugged on the scarf he still insisted on wearing to get his attention.

"FRISK! ARE YOU ENJOYING YOURSELF TODAY?" Papyrus said, loud as ever. "THE GREAT PAPYRUS IS SETTING UP A FEW PUZZLES FOR THE ENJOYMENT OF EVERYONE!"

Frisk grinned, but began signing rapidly, asking Papyrus for a quick word in private. They would have asked Papyrus about this earlier, but the skeleton had been having so much fun planning the picnic Frisk hadn't wanted to interrupt.

Now, though, with everyone's music so loud, twisting through the air in chorus, they couldn't wait any longer.

"OF COURSE, LET US GO INSIDE AND CONVERSE!" Papyrus agreed, scooping Frisk up and carrying them into the house.

Frisk was signing again as soon as the door was closed, assured that they were alone for the moment. Papyrus watched intently, Frisk's question short enough he didn't have a chance to interrupt.

"MY BROTHER...USED TO SING," he admitted when Frisk gazed up at him intently, hands lowered. "IT'S...HARD TO REMEMBER," he continued, softer, looking into the distance as if the memories were there for him to see. "BEFORE THE RESETS, AND BEFORE HIS HOPE FELL SO LOW. I DID NOT EVEN REMEMBER HEARING HIS VOICE UNTIL HE ADMITTED HIS KNOWLEDGE OF THE RESETS TO ME. I THINK HE GOT TIRED OF EVERYONE'S REACTIONS AND HAVING TO GO THROUGH THEM AGAIN AND AGAIN, TOO," he added almost confidentially.

Frisk frowned, looking down at their hands sadly. They'd hoped maybe, since they'd promised there would be no more resets, everyone would be happy now.

"DO NOT BE SO DOWNCAST, HUMAN!" Papyrus exclaimed. "I AM SURE MY BROTHER WILL COME AROUND SOONER OR LATER. HE IS HAPPIER NOW, I AM SURE OF IT! THESE THINGS DO NOT GO AWAY IN A DAY, EVEN FOR SOMEONE AS AMAZING AS THE GREAT PAPYRUS AND HIS BROTHER!"

Frisk wasn't so sure, but they let themself be carried back outside anyway. Pushing the matter wasn't going to help anybody.

The picnic wrapped up a few hours later, as the sun went down and the skies went dark.

Everyone began to gather their things in preparation for heading to their own homes, hoisting tired children up into their arms and cleaning the backyard.

They all paused as the first stars began to appear.

It was hard to tell who began the song, but soon it seemed that nearly every monster was singing, a wordless chorus that their SOULS harmonized with, a hymn of gratefulness and joy.

Silently Frisk wandered among the monsters, his new family. They knew, if they wished, they could sing with them – they didn't like to speak, but it was almost easy to sing when the music resonated deep within their SOUL like this, calling for a response. But this moment was for the monsters, not them, even if they had been the reason the monsters were on the surface now.

When Frisk reached the edge of the yard, they thought they heard a new voice, soft and low. Curious and determined to find out, they crept closer.

Even if their voice had come easily to them, Frisk wouldn't have been able to find the words to describe how they felt when they peered around the tree and realized it was Sans, singing too softly to be heard among the rest but still singing with them. His head was tilted back, looking up at the stars, and Frisk could feel Sans' SOUL throb from where they hid.

Sans glanced back, seeming to sense his audience. His song stuttered and Frisk darted from their hiding spot to grasp his hand, silently pleading that he keep singing.

When Sans still hesitated, Frisk opened their mouth and finally let themselves join the song, quietly, still holding Sans' hand.

Sans laughed softly and gave Frisk's hand a squeeze in return before turning his gaze back to the stars. A few seconds later his voice joined Frisk's, a soft descant of growing joy and healing.

They stayed like that until Frisk shivered, finding themself wrapped up in Sans' hoodie a second later, tucked up against Sans' chest. Humming with quiet joy, they snuggled down and the two stayed on their hill until the song faded away, slowly making their way back to the house only then, when everyone else had left and their family was starting to call for them.

Healing was slow, but suddenly, Frisk was sure everything was going to be all right in the end.