New York Mets closer Edwin Diaz's walk-out song, "Narco," sounded a little different on Wednesday ... 'cause Timmy Trumpet was there to perform a live rendition of his song, right on the Citi Field grass, and it was awesome!

It all went down during the Dodgers and Mets game in Queens ... when New York called on their star relief man to seal the deal in the ninth inning.

Baseball fans know the 28-year-old pitcher's entrance song is "Narco" by Trumpet ... and lucky for Mets fans, the Australian musician happened to be in NYC.