What do you call a baseball player who sings?

The humor in this joke comes from a clever bit of wordplay, specifically a pun. It takes a well-known baseball term and twists it just slightly to create a new, silly image. The joke plays on the similar sounds of "pinch hitter" and "pitch hitter," creating a delightful crossover between the baseball diamond and a concert stage.

In baseball, a "pinch hitter" is a player who is sent in to bat in place of another player, often in a crucial situation to try and get a hit. It's a strategic move made by the manager. The twist comes with "pitch hitter," which conjures the idea of someone who not only hits a baseball but also hits all the right musical notes. The word "pitch" serves a dual purpose here, referring to the ball thrown by a pitcher as well as the melodic quality of a singer's voice. It's a funny mental image of a player belting out a tune while waiting for a fastball.