Singing off-key in front of others is one way to get embarrassed. Regardless of how you get there, why does embarrassment almost inevitably come with burning cheeks that turn an obvious shade of red (which is possibly even more embarrassing)?
Blushing starts not in the face but in the brain, though exactly where has been debated. Previous thinking often reasoned that the blush reaction was associated with higher socio-cognitive processes, such as thinking of how one is perceived by others.
After studying subjects who watched videos of themselves singing karaoke, however, researchers led by Milica Nicolic of the University of Amsterdam have found that blushing is really the result of specific emotions being aroused.
Source : https://arstechnica.com/science/2024/08/karaoke-reveals-why-we-blush/