They say that the secret to engrossing music lies in constantly surprising your listener by violating their expectations. The harder they find it to predict which note or lyric comes next, the more the song will engage them. That is, as long as the sequence is not so discordant as to pull them right out of the song. The ideal song leaves the listener feeling like they could have guessed what would have come next if they had a bit more skill or experience. Captivating music induces a flow state.
How would you do this in other mediums? With other tasks?