How can one learn to harmonize by ear effectively?

Learning to harmonize by ear effectively involves practicing listening to different melodies and identifying the harmonies that complement them. This can be achieved through regular ear training exercises, such as singing along with a melody and experimenting with different harmonies. Additionally, studying Music Theory and understanding chord progressions can help in recognizing harmonies more easily. With consistent practice and a good ear, one can improve their ability to harmonize by ear effectively.