Among the instrument groups and within each group of instruments, there is a generally accepted hierarchy. Every instrumental group (or section) has a principal who is generally responsible for leading the group and playing orchestral solos. The violins are divided into two groups, first violin and second violin, with the second violins playing in lower registers than the first violins, playing an accompaniment part, or harmonizing the melody played by the first violins. The principal first violin is called the concertmaster (or "leader" in the UK) and is not only considered the leader of the string section, but the second-in-command of the entire orchestra, behind only the conductor. The concertmaster leads the pre-concert tuning and handles musical aspects of orchestra management, such as determining the bowings for the violins or for all of the string section. The concertmaster usually sits to the conductor's left, closest to the audience. There is also a principal second violin, a principal viola, a principal cello and a principal bass.