That's true Man. My pianist at least listens to what I got to say. But he rarely changes the notes for the song if I'm the one to tell him. But the best way to go about it is to add whatever you could to make the song sound better. Be sure to put your input as far add-ons. And you have to have a humble spirit when it comes to situations like that or else you are playing for the wrong reasons. It's very hard to stay under submission when it comes to things like that. But the only option that I could think of recommending you is to contribute to it as much as you can.
What I think pianist fail to realize, especially the ones who don't read music, is that when you change a song, it should only sound better, not worse or degraded. When a pianist changes a song, it only takes away from the groove or the song. Cause there is always a great reason why the person who wrote the song, wrote it the way they did. Cause most gospel songs are written just to assist the singer or choir, and follow what they are saying. When you a pianist changes that, it takes away from the purpose of the musicians playing, which sucks. And especially if they don't read music, the only reason why they would change the song is because they don't know how to play it correctly. So I sort of find them changing the song as an excuse.
The director for one of the choirs I play for at my church, loves changing the keys for the song. He usually does it to go easy on the choir. When in the back of my head I'm saying, "Make the choir strain to hit those notes". Cause if you change the key to go easy on them, when it comes time for them to sing a song that you can't change the key to or it won't sound right, you are lucked out cause you have physically lowered their vocal range. So, as a bass player noticing the falling of a band or choir is a very sad view, cause if they don't budge, you going down with them. You feel me?
Anyways, just do what they pianist say if you want to stay away from controversy!
- Big Dad-E Bass