1) Bad men of opera, often 2) Bad men of opera, usually 3) Boris Godunov leads 4) Boris Godunov singers 5) Chaliapin and Moscona 6) Chaliapin and Pinza 7) Chaliapin and Pinza, notably 8) Cheek and Foldi 9) Choir voices 10) Deep opera singers 11) Deep opera voices 12) Deep operatic voices 13) Deep vocalists