Finally, because each instrument and voice has distinct dynamic ranges, when they play or sing together, there must be an awareness of balance in the simultaneous volumes. If the singer is the most important sound, it needs to be louder than anything else. If the guitar takes a solo in the middle, but plays chords before and after, a volume change should happen to bring the guitar out from the mix when it is the dominant part of the whole. Balancing the volumes between voices and instruments is the responsibility of both the musicians (the singing and instrumental kinds) and when using a sound system, the sound engineer. If the concert is purely acoustic (non-amplified), then the performers are responsible for the balance. If the concert is amplified with a sound system, then the sound technician behind the mixing board provides the evaluative “ears” for balance.
Volume in music is easy for the listener to understand, but balanced and appropriate volume is sometimes difficult for the performers to attain.