Something I learned while making this synth is that some single-tone sirens can have a faint dual-tonality to them that makes synthing them a bit more challenging. For single tone P-15s and Banshees (8 port), the trick is to add in two supplemental frequencies alongside the main 460 Hz, 230 Hz and 920 Hz. That way, the synth will sound MUCH more realistic. Just make sure the two supplemental frequencies are under -22 dB peak.
https://www.youtube.com/watch?v=piUqV6owESk