Almost any reissue of material that has already appeared on CD in an earlier generation. Compare the post-millennial CD remasters of Slowdive's Souvlaki or the Cocteau Twins discography to the original CD issues of those albums in the early 1990s. Generally anytime an album is announced as "newly remastered" these days, the sole significant change is decreasing its dynamic range.

Any examples that I can listen to online?