From the UK Daily Mail:

One mother seems to have found the secret to changing her baby’s mood in an instant – she uses the power of Katy Perry.

Read more: http://www.dailymail.co.uk/news/article-2716331/Adorable-moment-crying-little-girl-completely-transforms-hears-Katy-Perry-come-car-radio.html#ixzz39XY9F8P3