premise: A brass quintet is playing music. hypothesis: Five people are playing metal instuments.
entailment: A quintet is a group of five people; a brass quintet is a group of five people with brass instruments.  Brass is a kind of metal, so a brass quintet is a group of five people with metal instruments.  Playing music with instruments requires playing the instruments; as the brass quintet has metal instruments, they are a group of five people playing metal instruments.