Is it true that a deceased young man (from the age of puberty to 25 years old) has music played for him and is mourned with ululations, and is this considered an innovation (bid‘ah)?

It is not permissible to accompany the deceased with music; rather, it is forbidden. And believing that this is obligatory is a grave innovation (bid'ah), because it is believing in the obligation of something that Allah Almighty has forbidden.