changing alarm siren chirp

I was messing around with the siren that came with my 5902 I think its the 514N soft chirp. I opened it up and was cutting the tone jumper wires to get rid of some of the tones I didn't want. While testing it on my bench power supply I found that the stock chirp sound (arm/disarm) is achieved by a very fast momentary 12v pulse to the siren (nothing new here) buut if that pulse is just a few milliseconds longer it sounds completely different and much better in my opinion (I picture someone arming a Ferrari or lambo when I hear it) Anyone do this before or modify the input signal to give a slightly longer pulse?   I couldn't find anything through a search.

ha I know I was just curious how they did it if they did.    I dont have my alarm installed yet so I cant simulate the actual pulse of the alarm quite yet. I was thinking the proper capacitor and resistor across the line might do it.