Technically easy (velocity, figuration, etc.), but not "musically" easy.I have no idea how to elaborate on this, so someone else will come along (or slap me silly across the face if I'm completely wrong).Actually, I do have an example. Chopin Nocturne in C minor, Op. 48-1. Relatively "easy" to pull off playing the notes, but playing it well is a different story.Quoted from a thread: "Sustaining a musical line on top of a row of chords at pianissimo is not easy."Things like that make some relatively slow pieces difficult.