Do one-part horns not exist anymore?

While testing a one-part horn I made recently, it acted like a two-part horn and required me to hold the "h" button to play the whole sound, rather than the whole sound playing when the "h" is tapped. "two-part" is set to "0," so I'm not quite sure what's going on. Do one-part horns not exist anymore? Trainz 2019.

Glad you mention it. Some time ago I mentioned it here at the forums, but had no response. At helpdesk I was given washy answers, and so life goes on... So I admire your braveness for bringing the subject.. again.