4 Pots, a momentary push button for triggering style, a toggle switch between permanent on siren and the push button.
two other switches with different capacitance, giving different oscillations.
Sounds like quick rising sirens are abound in this add on siren, that complements the other already shown

Testing it with the delay around the HT8972 IC ( cheap enough to have in a siren, at least if you want a budget thing).