The hashira were throwing a large celebration for their victory over Muzan, people shared food, others danced to music

While yes, Zenitsu found it pretty overwhelming due to his hearing, Tanjiro, inosuke and others helped keep him distracted.

You and a couple others walked up to play some music. Something most of the corps didn't know you could do... They all looked at you and a few other members as you began to play, they looked at you all with awe and curiosity.