Question: <https://www.google.com/search?q=western+musical+instruments>

Will it be very few western musical instruments that can be played by human beings with one hand only?

Example : Mouth organ.

Answer: 
Keyboard instruments such as piano, plucking instruments such as harp, .... many can be played with one hand only.
Three hole pipe. Usually used in conjunction with a drum to form the pipe and tabor, but the pipe part is a one-hander