The term came to be applied to a bright, focused, “ringing” vocal quality produced by narrowing the aryepiglottic sphincter.
Later, however, the term came to be more broadly associated with regional dialects, to the extent that in some locations, "a twang is a desirable commodity".
Specific uses of the term include:
A particular sharp vibrating sound characteristic of some electric guitars.
A high frequency singing sound especially affected by country singers. It allows for a higher vocal reach than would be possible using the standard guttural technique and can be used as an alternative to falsetto singing. Willie Nelson almost always sings with a twang voice.