Angor already knew the trick. However, currently in his early stage after learning the cantrip, he had to stay fully focused at all times. Any distraction would cause the illusion to fail.
If he could use simple sound to trick someone and inject terrible terror into their mind, the effect of Melodious Illusion would grow tenfold and become deadlier. However, to achieve that, he had to learn how to manipulate the minds of people, which he still had no clue yet.
"Man… the more I get into illusions, the lesser I feel about myself in this world," Angor sighed. "Alright, let's get to the quests. What did you find?"
Dave passed his bone card to Angor. "Every subject is like this. Alchemy isn't an exception."
"Alchemy? I don't have much problem yet," Angor was looking at Dave's card and only replied absent-mindedly.