Actually, I just noticed that this thread was asking how "musical critics" can improve. Does this refer to critics that happen to be musical? Or perhaps, even more radically, to people who present their criticism in musical form?

I like the idea of the latter, as I've always thought that artists themselves are art critics: strong musical statements are implicit criticisms of vapid ones. The fantastic improvising saxophonist John Butcher said something along similar lines in a recent interview in The Wire magazine: that his playing is the vehicle of a rejection of other forms.