Maria
"Okay, Leon." He said, grinning and standing up to go pick a song. He decided on How A Heart Unbreaks and got ready to sing. Once the lyrics popped up on the TV, he matched his voice perfectly with the tone and notes. Seems like he knew this song really well. His voice was ultimately really good for someone his age. His demeanor completely is the opposite of his personality. He usually seemed bored, and somewhat a blank slate. But when he was on stage, he was passionate and full of energy. He would show his true self, dancing and giving off a powerful yet respectful aura.
Jacqueline
As Victor sang, Nessa bobbed her head along, listening to the words to a song she hadn't exactly heard before. While she did, she went out to grab some snacks, since she at least, hadn't eaten yet. She came back during what was probably the most intense part of the song, and danced a little to the background music. "Hey boys, I brought snacks!" She announced.

"Ace! L-leon nd I...'re kinda starving..." Allister sighed, before Nessa sent a chocolate bar flying his way, which smacked him in the face. Followed by her dropping a bag of chips in Leon's lap. Vic had just about finished his song, and she clapped, "Whoo!" Along with Allister who seemed to gently applaud along with her. 
The boy was still looking around for a way to get out, but couldn't really figure one out yet...
He supposed he could ask to use the bathroom and slip out that way? Yeah, that was an option! Then he could just go back to the mansion and chill for the rest of the night.
"Alright! Who's next?" Nessa asked.
"Can I go to the b-bathroom!" Allister more demanded. Nessa just looked at him, before turning back to the boys. "Ehem, who's next?"
Jason
"WOO!" Raihan brought out the maracas and played along with Victor. His voice was decently good and while the guy always seemed like a try hard at looking uninterested in things, he's really spreading his wings now! "Good job, man! That was nice! Nice one!" He puts down the maracas once the protagonist was done with his singing and clapped. Nessa had apparently gotten snacks and Raihan looked for something healthy within the pile. "Next one is you, Lee!" He slaps the champ at the shoulder to get his attention—since he's already gulping down those chips Nessa dropped him!

So as for Leon, before the chips were given to him, he also played an instrument along with Victor's singing—a tambourine! It really was fun just banging the thing along to the beat of the music, while hearing this snarky guy in front of him use his voice for singing. Leon smiles up at Victor once he was done. Okay, and *That's* When the Galar man attacked the chips at Arceus-speed. He choked when Raihan smacks his shoulder and he stands up abruptly as if he was anticipating this! Leon didn't really want to sing since it's something that just seemed silly to him. But if he doesn't want to lose and pay for the snacks, well—

The champ grabs the mic from Victor and select his song. "Listen well!" He yells into the mic, having both hands holding onto it. The song would start and Leon turns toward the screen to read the words and get the timing right... "Just a small town girl—" His voice is quite hearty, hitting a good bass, but carries smoothly into the air as he sings.