Squeal is due to a part vibrating.
With brakes this is common; the pad sticks, the arm twists[1], the pad slips, the arm untwists, repeat three thousand times a second.
When the frequency is a good match for the arms' resonant frequency you get squeal.

Change either the stick-slip nature ("new pads"[2]) or the resonant frequency (adjust pivot clearances) and the squeal may change enough to disappear[3].

[1] or moves on the pivot, or some other small motion happens
[2] what you just did
[3] or appear