So I was watching this footage of Wind Waker HD and I noticed something different about the background music - not the melodies themselves, but the instruments/soundfonts. So I made a comparison of the original Gamecube tracks with clips taken from the HD footage.

The first clip you’ll hear in each pair is from the Gamecube version’s OST, and the second is the HD clip of approximately the same part of the song. Listen in particular to the violin in the Wind’s Requiem, the organ in the Gohdan clip, and the percussion in the Forsaken Fortress track - they all seem to be either live recordings or higher quality soundfonts. The quality shift is subtle, but it’s definitely there.