sort of, the craft. - and when we go to london to study, or to the conservatoires, _ you can see the difference between welsh singers. . they've just got some sort of, i guess, confidence. - he sings in welsh so watching you judging these voices, what do you look for in a voice? well, i think for me it is the tone quality, and how the vowel sounds that they create is one of the most key things for me, is how the voice, sort of, resonates, and also the way that the voice works with text. i think that's really, really important. and of course, that's what bryn terfel is fantastic at doing, as well. now, you know sir bryn terfel. just describe his voice for us with your musical knowledge. what makes it so great?