The engineer is in charge of recording the musicians in the recording studio. He is responsible for recording, mixing and mastering the recording as well as supervising the other workers in the studio.
An engineer's assistant helps in the recording and mixing process, and sets up and tears down the equipment such as microphones and instruments.
The owner of the recording studio is in charge of the financial end of the studio, booking musicians and clients, and supervising all of the studio's employees.
Musicians can work as session musicians, where they record backing tracks, TV and radio jingles, and movie soundtracks.
Recording studios will also have in-house arrangers/composers who write music and lyrics for solo acts, commercial jingles and show/movie soundtracks.