Psychological research believes that music is one of the three common factors that trigger nostalgia. Wearing the mask of "fans", the society fears to sing loudly.
After the atmosphere of "de-individuation" dissipated, everyone picked up their identities again and returned to real life. Nostalgia is a bittersweet desire for the past, which may include positive emotional experiences such as yearning for the simple life of the past. But overall, there will be more positivity in loneliness in the post-90s.