I went to a show in LA back in the early 90s.
It was Los Lobos, The Blasters, and X.
About half way through X's set, Billy Zoom's
Guitar broke a string.
Now I've seen X many time's, and never seen Billy play anything other than his vintage silver sparkle Gretch. It must be the only one he has, because instead of a roadie running in with a replacement guitar, he reached behind his amp, grabbed a string and started replacing it mid show.
Now a hopped up punkrock crowd, including a mosh pit, isn't gonna wait patiently while you re-string a guitar soooo....
John Doe steps up to the mike and launches into a fierce version of " Black Betty".
Just bass, drums, and vocals. It was badass!
The crowd didn't blink, maybe didn't even notice. When the song was finished, Billy was re-strung, tuned up, and ready to rock.
That's how pros do it.