It's fairly complicated to translate to the format the plugin, and I can't read sheet music. Someone else out there may have the expertise to get it done much quicker, and it seems like the North American style siren(s) would be appreciated by many users of this plugin.

Anyone want to take a crack at it? It'd be great to have a yelp and hi-lo 😄

Here are 2 MIDIs (the second has multiple siren tones on separate tracks, fire truck horn, etc) - hope it helps!
https://www.dropbox.com/s/pvjebrtyyvspmob/Siren_Noise.mid?dl=1
https://www.dropbox.com/s/6ql9th6pwh9o82o/Emergency_Sirens_in_Why.mid?dl=1

Hi there,
that's also what I think. The North American style sirens would be a great addition. Like you I am not able to read sheet music and don't know how to translate that kind of a siren into something which sounds like you would expect it to.
I just wanted to append that I am absolutly willing to support any effort put into this topic. For example add support for more/multiple instruments with different tracks if needed.

Another thing that was suggested is the support of direct MIDI playback. This is a very interesting thing, but I currently have no idea how to do this. So it won't be a thing in the near future, but I will definetly keep it in mind. 

Thank you for that post and the support of this plugin.

Best regards
ZockiRR