If you're a musician and you find out that your instrument has broken just a day (or a few hours) before you're supposed to perform with it, taking these steps should allow you to handle this stressful situation.
Rent an instrument instead of borrowing one
In this situation, you should not look for a friend or another local musician who can lend you their instrument. Instead, you should find an instrument rental company and order the one you need from them. If you do this, you will have a large selection of instruments to choose from and you may, therefore, be able to find one that is similar to the violin you normally play (or one which is very similar).
This matters, as it can take a while to get accustomed to playing a different make of instrument. For example, if the finger placement for the violin you borrow from a friend end up half a millimetre away from where yours does, you might automatically put your fingers in the wrong positions and end up playing the wrong notes sometimes.
As such, if the violin that a nearby musician offers to lend you is not similar to one you have ever used before, your performance that you give whilst playing it might be quite poor because you won't have enough time to get used to it. Conversely, if you rent an instrument that is the exact same or very similar to your own one, you should not have any trouble using it.
Extend the rental period for a week or two beyond the performance date
It's best not to just rent the instrument for the day of your performance. If possible, you should rent it for a week or two after this event. The reason for this is that you might have to wait several weeks for your original instrument to be repaired.
If you return the rented instrument immediately after the performance, then you might not have any instrument to practise on whilst you're waiting for your own one to be fixed. If you're a professional musician, missing out on this much practice could make your playing skills a little bit rusty. This could present an issue if you are booked to play at an event soon after your instrument is repaired and are expected to play a song that you are unfamiliar with. By extending the rental period for a few weeks beyond your performance, you can practice and ensure that your skills are still razor-sharp when you next need to perform.
Reach out to a shop that offers instrument rentals for more information.