I don’t know where else to start this discussion so I will post it here and would be happy to read your opinions.
I would like to bring your attention to their perfect pronunciation when all the three of them perform in English. I must say that I had never, never heard a singer, of any nationality, sing with such perfect pronunciation, accent, intonation and fluency in a foreign language. I grew up in France and England so I can be considered a native speaker in both languages, and I’ve taught linguistics and foreign languages in schools and universities for over 20 years, so as a linguist I have always been aware that one can never get rid of his/her native accent unless he/she grows up in the country from a very young age. This has to do with the way the brain works. Research has shown that children’s brains are developmentally ready to accept and learn a foreign language, and fluency comes easily, rapidly, and without accent. Between ages 8 and 12, a child loses the ability to hear and reproduce new sounds as they did when they were younger. That’s why I was truly astonished when I heard them sing in English. The amazing thing is that they have an Italian accent when they speak but not when they sing. A Spanish friend has told me that they sound native when they sing in Spanish as well. This calls for a case study! But it also shows how much work and proficiency they put into their craft.