One of my bikes has cantilever brakes on chrome rims. With dual compound Koolstop Eagle 2 pads braking is adequate and I can rely on the front brake at least in the dry.
The back brake squeals like a stuck pig. I could easily make it stop, but it's a much more effective warning than a bell or a shout when someone steps out in front, or when the lights change while passing stationary traffic. I like this feature.
I'll restrict this to dry conditions as wet rims obviously change the behaviour. I can drag the brake lightly without squealing, or lock up the back wheel, but intermediate braking almost always produces a loud squeal for quite a range of pressure. My issue is the almost. This morning was dry, and I tested over a number of stops without using the front brake. All were from around 20 km/h (10--15miles/hour) and were planned but fairly sharp stops. Excluding when I skidded the back wheel on a dirty bit of road, it squealed with no thought on about 80% of the stops. On the other 20%, no modulation could produce a squeal. Why?