An opera composer is a fellow who writes opera music.
In opera, the composer is the main guy.
He is viewed as the sole author of his operas.
That's because in opera the music is EVERYTHING - characters, action, scenery, the rage of the elements, etc.
There was once a play by Victor Hugo, a nineteenth century French playwright, titled "The King's Amusements.
" It was about this medieval French King, Francois the First, who made it a habit to seduce other people's wives (and/or innocent daughters) and then abandon them.
Those who disagreed with this mode of action ran the risk of having their heads chopped off.
He was a hell of a guy.
The story revolves around Francois's jester, Tribulett, and his beautiful daughter, whom the king seduced.
The jester swore to take revenge on his king.
Now this composer fellow, Giuseppe Verdi, an Italian, read the story and liked it.
He thought there was just about enough dramatic material in it to make a good opera.
So he asked his librettist, a fellow called Piave, to rewrite it as an opera libretto.
There was a problem with the story not being politically correct (in those days, it was called, simply, censorship), so Piave had to make some changes, moving the story away from the French throne and closer to home.
He turned the French king into an Italian duke.
He changed the lead character's name from Tribulett to Rigoletto.
And so forth.
After that, Verdi composed the music.
If you look at any opera program today, you'll see that "Rigoletto" is an opera by Giuseppe Verdi.
Not Verdi and Hugo, or Verdi and Piave.
In opera, the music is really EVERYTHING.