Which instrument is the odd one out?

Vibraphone
Marimba
Glockenspiel
Xylophone

Answertaxman;

Answerruth's dream is similar to mama"s, she wanted to build a happy family and believe one step toward this goal is to own a bigger and better place to live. also deferred by lack of money, which forces her and walter to live in a crowed apartment where their son, travis must sleep on a sofa///now one site said ruth wants to move to clyborn just keep that in mind/// good luck