Singing like a Broadway singer requires a daily commitment and the development of the voice through vocal exercises. There are several steps to begin to develop your voice safely and effectively. It is crucial that you do not push your voice to develop too quickly. The vocal chords are delicate and must be exercised over a long period of time to become effective. Learning to gain control over your voice means that you will be able to sing any style of music.
Start with a daily vocal warmup. Practice singing "hmm" by starting on a low pitch and gradually increasing the pitch. Complete this exercises on several different pitches to warm up your voice. This exercise should be used before singing any Broadway song.
Vibrate your lips by making a "brrr" sound. The lips should be buzzing but be loose enough to flap a little. Again, complete this exercise on several pitches. This will help you build strength in your voice to prepare you for Broadway music.
Sing scales on solfege syllables. Use a piano to play C. Singe a major scale on C with the solfege Do - Re - Mi - Fa - Sol - La - Ti - Do. The corresponding notes on the piano are C - D - E - F - G - A - B - C. Continue playing each scale by transposing each pitch a half step higher. Most Broadway music uses scales.
Practice vocal etudes that will help to develop and strengthen your voice. (See Resources)
Continue each practice session by singing Broadway songs that fit within your voice. Take your time learning these songs and use the piano to check your pitches.