the instruments of the orchestra are divided into districts: the strings, woodwind, brass and percussion. each section (group of instruments) will have a player who is the "boss". the principals will make decisions about seating arrangements, and about technical ways of playing the music: for example the principal of the string sections will make sure all the players move their bows up and down in the same direction. the violins are divided into first and second violins. the first violins usually have the tune while the seconds, most of the time, are part of the accompaniment. the principal of the first violin is the leader (or concertmaster) of the orchestra. in a professional orchestra they will be the most highly paid member of the orchestra.