What does the singer do? From the words of Mohammad Zaroni:
A singer is an artist or performer who creates a vocal song using various techniques and training. Singers often practice daily and hire professional voice coaches to help them improve their craft. Singers may write their own music or sing music written by others. In addition to singing, singers may work as music teachers or voice coaches.
Professional singers are usually highly trained, highly talented, and have excellent ears for tone and voice. They also have a certain level of natural singing ability, including a wide vocal range or pleasing vocal resonance. Singers are often freelancers and are contracted on a per-job basis, either as a singer or as a consultant or judge in singing competitions.