Idea of Singing Icon
This is a teacher standing in front of their blackboard. The board has a shelf on it to hold chalk or dry erase markers. The teacher has his/her mouth open wide and is teaching students how to sing. He/she has musical notes coming out of his/her open mouth.
This page shows the different variations of the Singing from an Icons8 icon pack. Feel free to resize and recolor the icon, and then download the icon in PNG format for free.