It’s super simple to warm up on the go! (Especially if you’re in a car, and not on a bus!)
If it’s early in the morning, start with a frog-sounding croak, with minimal pressure, and slowly raise your pitch.
Continue with humming, again with minimal pressure.
Next up is donkey lips, also known as lip trills. They warm up the lips and take pressure off the vocal chords.
To get your diaphragm engaged and working, do 20 seconds of doggy breath, which is essentially rapid inhalations and exhalations.
Continuing with the engagement of the diaphragm, start to use your button (found below the sternum) and start singing ‘ha’ for 5 notes descending, moving gradually up in pitch.
Next, start to move the tone to your face, singing ‘meow’ and making sure that it is coming from your nose (it’s ok to sound over-nasally in the beginning as you are getting used to placing the sound there).
Try some arpeggios, either on ‘meow’ or perhaps starting on ‘ba’ and ‘ma’ if you want to approach the highest note a little more lightly.
And remember, most importantly, be aware of how your voice feels; let your voice warm up, don’t make your voice warm up.