What I did try recently though, seems ot have worked a bit better
The squealing front brake, although minimal on my bike has been driving me mad. It is a bit like that old VW Golf advert, with the annoying squeak, which turns oul to be the passenger's earrings.
Anyhow, sort of done what ' Mouse' said and now my bike IS as quiet as a mouse !
Tried copper grease on back of pads- no different
Removed disk retaining bolts and applied grease sparingly to compression washers using a cotton bud . It then struck me that to absorb the singing vibration, I decided to apply some to the wheel mounting arms which the disk rests against- again very sparingly. At all times taking care that none gets on the disk. Bolts then tightened to 24Nm equally using a torque wrench, so that pressures are very even all round. Thread lock applied to bolts. Result blissful silence.
Now disclaimer- DO NOT do this yourself cos copper grease m a y affect seals and m a y gradually contaminate the disk so that you have total brake failure and lead to more of those shhh you know what threads. Also may not work long term....
I feel that better remedy would be an absorbent temperature resistant washer between the disk and the wheel, which allows the disk to 'float' a little. IMHO
p.s. I am aware of reported BMW teflon fix or something