You could say, "I like trumpets," but that sounds a little childish. Most people would say, "I like the trumpet." Here, "the trumpet" isn't referring to a specific trumpet, but rather it's referring to a specific (type of) musical instrument (the trumpet) as distinguished from other musical instruments, such as harps and guitars. The same thing goes for violins and drums. Note as CJ Zwaan points out, for drums, you can also say "the drums" as it usually refers to drum sets.