I have dwarfism. If I wanted to volunteer to teach basketball to the youth group, my offer to do so would be kindly declined. However, I could be the statistician or the manager.
Same goes for choir. If someone does not have the gift of a pleasant singing voice, there are still a myriad of ways to serve the Parish in general and music ministry in particular. We always need AV techs to help with the livestream of Masses and other events! Someone who cannot sing can learn to play an instrument, we ALWAYS need organists!