WHEN PERFORMING - How to harmonize background vocals.
Step 1.
Choose the harmonies closest to the melody if you are the only background singer. Second melodies are harder to process while singing and can often become single, drone notes if you are not careful.
Step 2.
Sing less forcefully than the lead singer. Unless you are singing a duet, your microphone should be turned down and extra reverb may even be added to your voice.
Step 3.
Avoid vibrato as much as possible. Your vibrato may not match that of the lead singer or other harmonizers, and this can easily ruin the sound of a performance unless it is done extremely well.
Step 4.
Blend with other singers. The intent of background vocals is to enhance the performance while still emphasizing lead singers.
Step 5.
Sing with confidence. Know your part well. It is often hard to hear yourself and other singers as well as you would like to, and you are likely to miss notes or become completely inaudible if you lack confidence. Plus, if you do not know your part well, you may jump into harmonies that are supposed to be sung by other vocalists.