Three musicians reportedly beat up two passengers on the city's U2 line shortly after 5pm, after one complained about the music being played by the brass and percussion ensemble, Der Tagesspiegel reported on Thursday.
After a brief argument, two of the musicians suddenly attacked the 45-year-old. When his 37-year-old friend went to defend him, the third musician hit the intervening man in the face with his trumpet.
He suffered a cut to the mouth and lost several teeth and had to be treated in hospital, while his 45-year-old friend escaped injury.
The belligerent musical trio made their escape at the next station, but police officers who had been called to the scene stopped them on a nearby street and arrested them.
The musicians are reported to be aged 20, 24 and 32, and have no fixed address in Berlin. They are to face charges of aggravated battery. The trumpet, which was broken during the incident, was confiscated as evidence.