In Japan, police only use a simulated mechanical tone. They have one that is a 4 second rise/fall and an 8 second one that holds the peak for a few seconds. They usually use this one when there's a ton of pedestrians. Their ambulances have a harmonic version of their hi-lo that's for similar purposes, plus some have a mechanical that they'll blast.
Fire vehicles will use a simulated bell tone for the same purposes in addition to their simulated mechanical.
FD and
EMS also use electronic voice annunciators saying a message like "ambulance approaching from the left, make way". LE speak over their PAs constantly to this effect.
Believe it or not, it works pretty damn well, despite the oceans of people at some crosswalks. Then again, their culture is just a teesny tiny bit different
.