a baritonist
A baritone hornist is a person who plays the baritone horn.
A baritonist is a person who plays the baritone saxophone or the baritone horn.
It's not named after a person. It's named after the musical register where it plays.
just that a marching baritone
A baritone guitar is a large-bodied, long-necked guitar which plays in a baritone range.
A person who plays the euphonium is sometimes called a euphoniumist, euphophonist, or a euphonist, while British players often colloquially refer to themselves as euphists.
diva, soprano, alto, bass, tenor, baritone
A "harmonicanist" is what a person who plays the harmonica is called.
that totally depends on the player person.... but usually the baritone
A person who plays Scrabble is called a Scrabbler. (unofficially)
A drummer or percussionist plays the drums.
accordionist