Go right ahead, Ron: I'm interested in hearing more about what you're doing. My perspective from the Men's Chorus of the black Baptist church we belong to is understandably different. For starters, we rarely sing from sheet music. That would drive a lot of people nuts who are sued to singing tightly arranged scores. When we occasionally do sing from sheet music, our Director will arbitrarily change harmony lines that he feels would sound better if done differently. On top of that, he may change a section of harmony line from practice to practice, and even sometimes within the practice. The next time you come to practice, he may change a not or two again.
That approach is perhaps why trained singers find it too frustrating, trying to sing black gospel. On top of that, some of the guys in the baritone section I sing in wander back and forth from singing the melody line to the baritone harmony, sometimes within the same song. While our director works long and hard to get each section to learn their harmony, he realizes that most of the men in the chorus are not formally trained and don't have a good ear for harmony. When one of the guys in the baritone section sings the melody for a line of a song, it just means that they're a second tenor for that line... :-)

Another great difference is that we have to be prepared to sing a song we may not have sung for many months, spur of the moment. Our Director will often decide to do a song based on a line of scripture used in the sermon. When he plays the opening introduction on piano (we never know what we're going to sing) if you're singing the lead, you'd better recognize the song after a few notes and head up to the microphone, running through the song in your head as you go. There've been times when our Director just played chords as an introduction without an obvious melody while I've sat there wondering why he was smiling at me until someone nudges me and says, "That's your lead."

All of this must sound completely foreign to being in a choral society and doing formal arrangements. It takes different skills. The emphasis in the Men's Chorus that I sing in is the message. When we learn a new song, we read the lyrics together a few times without a melody, just so that we absorb the message we are going to sing.
Spiritual harmony is probably even more important that musical harmony. That fits me fine, as a folk singer. I've heard folk singers get every word right and do elaborate, impressive accompaniments of instrumentals and never get the song.

Another thing.... plenty of another things.... Many of the songs we do require the lead singer to improvise lines of the top of their head. The Chorus will keep repeat a simple three or four word part of the chorus while the lead singer improvises lines over the backing. Only a few members of the Chorus can do that. I've had to make up words when I've forgotten them singing folk music enough times that I can do it pretty comfortably. The Director may keep the Chorus going a long time, especially if the congregation gets in the Spirit. You have to be able to keep singing another line as long as the Director keeps the Chrous going. Then when we finish the song, if the congregation is still wound up, the lead singer may be called back up to continue improvising. It's a heady experience. not for the faint of heart.

I've never sung in a choir where you have to read from sheet music, out of choice. I've leaned to read music fairly well over the years, but feel limited looking down at sheet music all the time. It's just a personal preference. I've met many wonderful singers far better than I am, who can't sing harmony unless they have sheet music to follow. That seems weird to me. What I do seems even weirder to them.

Different strokes for different folks.

Jerry