This is a question that never came to my mind.
Watch a Dutch Girl group attempt to do so. The music blocks out most of the vibrator sound, but I am guessing they each sit on a sybian-type device (or someone is below screen performing a very enjoyable task).
A female at an online site describes their attempt:
"Ever wonder what it would be like to sing while you climax? Look no further. The Dutch all girl band ADAM, released a video this week of an attempt to sing their latest single "Go To Go" while a vibrator is being used to make them orgasm. The song is pretty catchy, but you can't help but giggle along watching the girls trying to maintain their composure while being stimulated. If you listen closely, you can even hear the vibe in the background."