Also called a recording engineer, they are one of the people in the background when they are recording music. Your favorite music artist would not have been able to release their record label without them. It is one of the most common choices for students for their career, especially among the ones that are trained in the professional audio.
Often, the recording engineers are hired by the recording studios, and there are also times that they are freely open and even operate their very own project studios. They even act as freelancers sometimes and hired by producers or professional recording artists to go to their studio to start recording.