A person who plays the gong is typically referred to as a "gong player" or a "percussionist." The gong is a percussion instrument that produces a deep, resonant sound when struck with a mallet or drumstick. Gong players are skilled musicians who are trained in the techniques of playing the gong to produce a variety of tones and effects.
A "harmonicanist" is what a person who plays the harmonica is called.
A person who plays Scrabble is called a Scrabbler. (unofficially)
A drummer or percussionist plays the drums.
accordionist
Guitarist
harpist
a cymbalist
guitarist
A saxophonist.
a baritonist
A pianist.
The umpire is the person that rules on plays.