Hi there,
There are many factors to consider here:
1) Is the musician born again/ saved or they are just paid to play;
2) Is the musician a member of the church;
3) Is the impregnated lady in the same church? born again? in the choir?
4) Is there a code of conduct for the choir?
5) Who is accountable for the choir [is the MoM / choir director given enough authority to decide on the direction of the choir or is it the pastor that decides]?
6) What is the history of the person like if they are born again [your history can count for you or against you]?
Those are the questions that come at the top of my head.
As the doc has said, every decision must be ushered by prayer- prayer does change things.
Finally, whatever decision is taken, the decision makers must have a clear objective in mind [e.g., 1) we want to counsel the brother/& sister and help them to know the Lord better and not make the same mistake again, and they must help us to make others aware;
2) we want to rid the choir of non-believers, we want the praise team to consist of people who are saved and who want to live pure, sanctified lives;
3) We want to make sure that such a thing does not happen again by taking such [a,b & c] specific, controllable, measurable and wise measures that will not cause anyone in the church to stumble... etc]
With people like you in the church, I believe you have enough of God's wisdom to assist the decision makers to handle the situation properly.
Remember, nothing should be done out of strife [eg, trying to show the musician that the church has more power], but rather, it should be to discipline him with love [Rev3:19-20- the Lord Jesus rebukes those that He loves.] Show him and the lady why it would be beneficial for them to take whatever disciplinary measures imposed on them, versus trying to kick them out, unless if they are people with "independent spirits"...