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Hold a sustained note. Work on hitting high notes. Reach for low notes.

Article:
Sometimes songs require a singer to hold a note for an extended period, and if you aren't prepared for this or don’t have the right technique, you may not be able to hold the note for the full length. To practice holding a note:  Expand your ribs, tuck in your lower belly, and relax your shoulders and neck. Inhale slowly as you open your throat, arms, and chest, as though you were just surprised by something. Hold this openness while staying relaxed. This is the same technique you will use to hold a note. Now, choose a note in the middle of your range, repeat the above steps, but this time sing that note and hold it for as long as you can, keeping your throat open and relaxed as you sustain the note. If you’re going to be singing a song that requires you to hit some high notes, there are ways you can practice for this. The problem with high notes is that you can damage your vocal chords if you strain too hard to hit the notes. To reach high notes without causing damage, you need to:  Practice keeping a steady flow of air as you sing. Keep all your muscles relaxed. Keep all your resonance chambers (the throat, mouth, nose, chest, etc.) open as you sing. Pick a song with high notes and practice it in sections until you become comfortable with each section. Practice the song once through without singing the words: instead, vocalize a single sound to go through all the pitches. When you're comfortable with that, sing the song, words and all, through entirely. A song with low notes can also be difficult to master because with low notes, you can easily lose control of the sound, because your vocal chords relax as the pitch descends.  To maintain control of your lower notes, it’s important to keep your throat relaxed and maintain resonance in your face. If you stop feeling the resonance in your face as you reach for lower notes, shake your head from side to side to open your throat and try again. Don’t worry if your volume drops with the lower notes, because lower notes cannot be sung at a loud volume. Instead, focus on maintaining the tone and clarity of the note, rather than the volume of your voice.