There’s a reason why orchestras re-tune during performances. Instruments go out of tune within an hour or even less if a piece is particularly vigorous (especially for strings), or large crowds of people change the room temperature, instrument temperature changes after prolonged holding, etc. I realize it’s not always practical during Mass to do this, but after sitting through three long Masses/liturgies listening to string instruments slowly going out of tune and sounding like dying cats, and mentally preparing for Easter Vigil, if you’re working with more amateur string players, MDs may need to be more vigilant in managing their instrumentalists’ intonation.

For example our choir loft has both a washroom and a music storage room lined in sound dampening acoustic foam there’s no reason why a string player couldn’t excuse his or herself to briefly take a tuner with them into such a room and retune, even better, investing in a headstock tuner (they’re not that expensive) that uses string vibration to tune rather than microphones, so you can retune mid-playing in loud environments.

Failing that, maybe there’s a way to start a church musician scholarship fund to held fund private lessons for church musicians to increase their skill level.