Vocal refers to the part sung with the voice, or to the person singing it. Because it delivers the melody and the lyrics directly, it is the element placed most in front in many songs.
The basic idea
Pitch, rhythm, diction, breathing and emotional expression combine to create the impression of a vocal. What matters is an expression that suits the song, not perfect accuracy alone.
Recording and programming with it
Before recording, check tuning and vocal range, and record takes in short sections. Layering backing vocals in the chorus adds thickness.
How it differs from related terms
The vocal is the lead of the song, while backing vocals usually mean a part of several voices supporting the main melody.
To push the vocal forward, creating space where the words and the melody can be heard matters more than adding accompaniment.
