Basically, a Music Engineer sets up the recording equipment and records the musicians, making sure all the levels are set correctly so there’s no clipping. This includes placing the microphones perfectly and ensuring the surrounding area is ideal for recording.
Depending on your role in a given project, you may be required to mix the music in post-production using EQ, compression, reverb, delay, and other effects.
As an Engineer, you also want to make the artists feel at home and comfortable. Try to do what you can to make them feel special — it boosts their confidence and helps them play better and make more compelling music. Just generally put out some good vibes.
On the other hand, you don’t want to overstep your boundaries into Record Producer territory. Usually, a band will self-produce an album or hire their own Producer. But that doesn’t mean you, as the Engineer, can’t give your input on how things sound.