One terrible example is watching Woody Guthrie and Pete Seeger sing. They threw
their heads back and strained their vocal cords. Unfortunately many folkies
followed that model. It can lead to nodes, polyps, and loss of voice.

Excessive "belting" or shouting can lead to trouble as well. Some people have
cast iron vocal cords like the blues singers and gospel shouters but normally
this can be hard on the cords.

Many people try to sing too loud and lose the natural timbre of their voices.