https://www.musical-u.com/learn/how-to-sing-harmony-like-a-pro/
Do you have trouble hearing or singing harmonies?
Creating harmony with other human voices is great fun and can be a profound musical experience. If you can sing a melody in tune, you can teach your ears how to sing harmony lines as well.
Like most things in music, harmony singing is a skill that can be practiced and mastered.
Here are four effective (and fun) ways to learn how to sing harmony:
https://www.musical-u.com/learn/how-to-sing-harmony-like-a-pro/