The EMD E9 was the final model in Electro-Motive Division's long-running E-unit line of streamlined passenger diesel locomotives, built in the United States during the 1950s and early 1960s. This particular recording became known among Trainz simulator users after it was found inside the game's files, with uploaders noting that no specific locomotive in the game appeared to use it, which explains the unknown label. Shared on soundboards since then, it remains popular with railfans who want a clean, isolated E-series horn without background engine noise for their own routes and videos.