Praise be to Allah.
Playing songs and music loudly in cars is a kind of committing sin openly. The Prophet (peace and blessings of Allaah be upon him) said: “All of my ummah may be forgiven except those who commit sin openly.” Narrated by al-Bukhaari (6069) and Muslim (2990). This hadeeth contains a stern warning to those who commit evil openly and broadcast it and spread it and do it blatantly. This person who commits sin openly feels no shame before Allaah or His creation, so he must be denounced and admonished.
We ask Allaah to set the affairs of the Muslins straight.
And Allaah knows best.