Edge_Orchestra
Rock n' Roll Doggie FOB
I thought the pitch changes because Edge keeps strumming in between, hence breaking the signal and starting a new siren? Your video makes perfect sense though, it's Edge strumming and the fact that it always replicates the sound 1:1 that puzzle me. When you look at the strumming behavior in some videos, it looks like Edge has the control over the siren. Then again, that video you showed where he doesn't even touch the volume knob at the end does indicate that Dallas is involved to some extent.
By the way, awesome WH-1 at the end of the video
I haven't found a way where strumming regenerates the siren. Although, I suppose it's worth looking into.
One way could be if the siren was recorded and set up as a sample and the strum activates it? I suppose something like that is possible.
Ah yes... the Digitech WH-1. T'is a lovely beast.