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Start by making a basic “hmmm” noise in your throat in your lower range as you exhale a breath. Repeat this five to 10 times, then repeat the same sound with your mouth open for five to 10 breaths. With your mouth open, you should make an “ahhhh” noise. Humming is a great way to warm up and relax the muscles of your throat, face, neck, and shoulders, and it can also help you control your breathing. Once your voice is warmed up with basic humming, begin to warm up for pitch changes by humming do-re-mi up the scale and then back down. Start at the lower end of your pitch range, and when you complete one sweep up and down the scale, go to a higher key and repeat.  Repeat this for four or five ascending keys, then work your way back down those same keys. Lip trills, also called lip buzzing or bubbling, are an exercise that vibrates and warms up your lips as well as your voice. To create the lip trill, you close your lips loosely, pout them slightly, and blow air through them (think of making the sound of a motor or raspberry). Do this for two exhales, then start slowly shaking your head from side to side as you do three or four more lip trills. Repeat the lip trilling and head shaking, and as you do this make a “b” sound with your mouth as you do vocal sweeps starting with a high note and going low, and then coming back up. Make an “ng” sound in your nose as though you were just saying the final part of the word “sung.” Continue to make this noise as you do three to five pitch sweeps. Every time you go back up and down again, push your voice into a slightly higher and lower pitch range. This exercise helps you warm up the voice gradually, prevents over-exertion of the voice, and helps singers transition between their head and chest voices, which refers to the different places air resonates in the body when creating different sounds and pitches. Tongue twisters are great for articulation practice, and if you say them in different pitches and at different volumes, they can be a great way to warm up before singing. Some good tongue twisters to try out are:  Sally sells sea shells by the sea shore Teaching ghosts to sing Peter Piper picked a peck of pickled peppers Unique New York The tip of the tongue, the lips, the teeth Really rural The big, black-backed bumblebee Red letter, yellow letter

Summary:
Hum. Hum do-re-mi. Do some lip trills. Practice the siren song. Practice tongue twisters in different pitches.