I'm often contacted by singers asking how to make their voices stronger. Weak or breathy singing can be corrected. Read on.
There are two outstanding reasons for always singing with a weak or breathy sound.
1. Shyness. Often, when people who are shy sing, their sound is also shy. Since shyness comes from a fear of being judged by others, or a fear of standing out from the crowd, singing in front of people puts a shy person in a very uncomfortable position.
Singing softly is reflexive for very shy people. This is interesting, since the reason that person is up there singing is to be noticed and appreciated by others. It might help to know that many top performers suffer from extreme shyness, and yet have been able to overcome the problem, at least while they are performing.
One technique which can help this is for you to assume a different, more aggressive personality ("acting" a part) while singing. Usually, shyness can't just be overcome by trying not to be shy. It often takes extensive therapy and much dedication to change from shy to brave.
So, why not just work on being a good actor. This way you can take the pressure off while you are performing by doing what all good actors do, acting. Of course you have to practice doing this, and it takes dedication and work, but as your "character" emerges in songs, your voice will become stronger.
2. The second major cause of weak singing sound is much easier to fix breathiness. This is just what the term describes: singing with a "whispering" sound. Letting too much breath come through the vocal cords along with sound.
If this is your problem, work with these vocal exercises daily: Sing some short scales or a series of notes using the sound "ka". "Ka-ka-ka-ka-ka-ka" ("Feel" this sound up in your forehead, not down in your throat.) Then follow this up by singing the same notes using just an "ah" sound. Try to make the "ah" scale sound as bright and punchy as the "ka" scale.
Then sing this again, starting with the "ka"s and finishing with another vowel. "ka-ka-ka-ka---EE.........., etc. Make sure your throat remains very open when you sing the pure vowel. Don't push the range on this. Guys stop around middle C, girls an octave higher. The exercise should start around an octave lower. Stop when you feel any stress.
Then, sing a short song like "Happy Birthday" trying to continue the more solid sound you should have been getting with the exercises. Do this often and your voice should become more solid and powerful.