After completing 3rd dungeon, using the Pegasus Boots to get the Ocarina, normally you can speak to Marin with the Ocarina and she will teach Link the Ballad of the Wind Fish. I've spoken to her with the Ocarina equipped in all slots, but it does not seem to trigger the flag for me. I've also tried unequipping and speaking to her and reequipping and speaking to her. I've also going into a building and leaving and speaking to her, as well as resetting the game.
Marin will teach the Ballad of the Wind Fish after taking her to the walrus by the desert and speaking to her in Animal Village. Again not sure if this was intentionally changed or a bug.
After completing 3rd dungeon, using the Pegasus Boots to get the Ocarina, normally you can speak to Marin with the Ocarina and she will teach Link the Ballad of the Wind Fish. I've spoken to her with the Ocarina equipped in all slots, but it does not seem to trigger the flag for me. I've also tried unequipping and speaking to her and reequipping and speaking to her. I've also going into a building and leaving and speaking to her, as well as resetting the game.