If you have a heart for the musicians but don't sense a call to be one, maybe your role should be intercession. Perhaps your interest is meant to stimulate prayer for them rather than a position on the stage for you. If you feel you are supposed to be in the band but someone else has your place, go to God and ask Him to bring discernment and wisdom. It has been my experience that God will make a way for you to be there if it is truly His will. Be careful not to pray against that person, even if you believe they are being insensitive to what God is wanting to do.
Nothing is a greater test of our character.
Either we will rise up in jealousy and jeopardize our own calling, or we will rejoice with our brother or sister over God's choice and blessing. Jonathan is a good example of someone who had the right response to God's choice of someone else. Although it would have been easy to feel threatened by the prophecy that David would be the next king instead of him, Jonathan instead committed himself to doing everything he could to make David successful. He has a wonderful role for you to fill in His body, a role fashioned especially for you. As you seek Him, He will show you what it is.