Location: Shaolin Temple
Prerequisite: Complete Hui Da the Strange Monk II, Affinity 60+
Petitioner: Hui Da
Reward: Spring Thunder and Dragon Roar
To trigger this side quest you need to complete Hui Da the Strange Monk II. You also need to raise Yi's Affinity with Hui Da to 60 or more. Hui Da's tastes will rise, forcing you to track down higher-quality musical instruments as Gifts. The NPCs wandering the world map are a good source of these items, and you can always buy more flutes from the Pawnshop in Pingkang City.
Speak to Hui Da once you activate the quest (save and reload your game once he reaches 60 Affinity) and he'll ask for Yi's advice. Yi is no musician, however, and so Hui Da asks a different favor: Fetch Zhang the Scholar, an NPC over in Pingkang City.
Travel southwest to Pingkang and walk west, sticking to the south end of the path. There are two houses in the west, and Zhang the Scholar is standing outside the house on the left. Speak to him and he'll join the party as a guest. Take him over to Hui Da to complete the quest, then speak to Hui Da again to receive your reward.