King's Quest

The name of this trophy is a little bit deceptive. It implies (at least I thought) that you had to blow on each of the horns you find throughout the Chapter. It turns out that is not so, you only need to blow on one horn but a great many times.

The horn to unlock this trophy on is located directly south of the center of town. You can access the area relatively early in the game but for sure can do this when you are questing for the Eye (or anytime after this quest).

From the town square, keep heading South (down) until you reach a very picturesque screen containing an orange looking horn on the left overlooking some water. Walk up to the horn and interact with it (X) to see Graham attempt to blow the horn and Old Graham to make a comment. You need to interact with this horn a grand total of 9 times, but ultimately you will unlock the trophy on the 9th time (and be greeted by a great nod from the game developers).

Note: you can accomplish this without having any of the horn mouthpieces. This particular horn requires Waddles' mouthpiece to activate the bridge.