They have amazing voices, and as far as I know they write their own songs & play instruments and whatever... (well I'm not so sure about all of them but whatever).
- John Mayer: The Heart of Life, Love Song for No One, Gravity.
- Adele: Melt My Heart to Stone, Cold Shoulder, Tired.
- Amy Winehouse: You Know I'm No Good, Back to Black, Me & Mr. Jones.
- Duffy: Mercy, Breaking My Own Heart, Distant Dreamer.