Violinist Ray Chen was onstage at Benaroya Hall performing a concert with the Seattle Symphony when a string on his violin snapped right in the middle of his solo. Here's how he and the orchestra handled it.
Thanks, Mike. Reminds me of 14 year old Midori, who broke an e string twice in the same concert at Tanglewood, with the BSO and Bernstein conducting in 1986. She had to do two violin swaps in the same piece. Added to that, she had to switch from her 3/4 sized violin to a full size violin. She was playing one of Bernstein's pieces, the Symposium. Apparently string breaks do happen and violinists do practice for it. They exchange with the concertmaster, who is sitting closest to them. Two string breaks, however, is much more unusual, especially when the violinist is not playing a full size violin (so the distance between notes is slightly smaller in her violin than in a full size one. You lose all the muscle memory cues from the hundreds of hours of practice and have to adjust the finger spacing (remember violins have no frets) based on hearing each note.
I remember attending a concert of the Vienna Philharmonic in Berkeley back in 2014. They had a few spare violins hanging on the backs of chairs I think for such an event occurring within the orchestra. Hard to do with double basses.